meaning of placenta presentation

Appointments at Mayo Clinic

• Pregnancy week by week

Placenta: How it works, what's normal

The placenta plays a crucial role during pregnancy. Find out what the placenta does, issues that might affect it and how it is delivered.

If you're pregnant, you might wonder what exactly the placenta is, what it does and what might affect it. Here's what you need to know about this important organ.

What does the placenta do?

The placenta is an organ that forms in the womb, also called the uterus, during pregnancy. The placenta is connected to a developing baby by a tubelike structure called the umbilical cord. Through the umbilical cord, the placenta provides oxygen and nutrients to a developing baby. It also removes waste from the baby's blood.

The placenta is attached to the wall of the uterus. Most often, it attaches to the top, side, front or back of the uterus. Rarely, it might attach in the lower area of the uterus. When this happens, the placenta may block the passage that connects the uterus to the vagina, called the cervix. If the placenta is near the opening of the cervix, it's known as a low-lying placenta. If it partly or totally covers the opening of the cervix, it causes a condition called placenta previa.

What affects the health of the placenta?

Various factors can affect the health of the placenta, including:

• Age of the pregnant person. Some conditions that affect the placenta are more common in older people, especially after age 40.
• Water breaking before labor. During pregnancy, the developing baby is surrounded and cushioned by a fluid-filled layer of tissue called the amniotic sac. If the sac leaks or breaks before labor starts, it's known as the water breaking. This raises the risk of problems with the placenta.
• High blood pressure. This condition can cause less blood to reach the placenta.
• Being pregnant with twins or other multiples. Being pregnant with more than one baby might raise the risk of some conditions related to the placenta.
• Blood-clotting conditions. Typically, blood hardens into a clump to help control bleeding from cuts. This process is called clotting. Sometimes, blood clots form inside the body and lead to medical problems. Conditions that cause blood to clot too little or too much raise the risk of some conditions related to the placenta.
• Past surgery on the uterus. C-section, surgery to remove tumors called fibroids and other uterine surgeries raise the risk of some conditions that affect the placenta.
• Previous conditions that affected the placenta. The risk of having medical issues with the placenta might be higher if you had problems with the placenta during a past pregnancy.
• Substance use. Some conditions that can affect the placenta are more common in pregnant people who smoke or use cocaine.
• Injury to the stomach area. A blow to the stomach area makes the placenta more likely to separate from the uterus too soon. Risk factors include trauma from a car accident or a serious fall.

What are the most common conditions and concerns?

Placental abruption

The placenta is a structure that develops in the uterus during pregnancy. Placental abruption occurs when the placenta separates from the inner wall of the uterus before birth. Placental abruption can deprive the baby of oxygen and nutrients and cause heavy bleeding in the pregnant person. In some people, early delivery is needed.

Placenta previa

The placenta is a structure that develops in the uterus during pregnancy. In most pregnancies, the placenta is located at the top or side of the uterus. In placenta previa, the placenta is located low in the uterus. The placenta might partially or completely cover the cervix, as shown here. Placenta previa can cause severe bleeding in a pregnant person before or during delivery. A C-section often is needed.

Conditions that can affect the placenta include:

• Placental abruption. This is when the placenta partly or completely peels away from the inner wall of the uterus before delivery. With placental abruption, the developing baby might not get enough oxygen and nutrients. The pregnant person might have back or stomach pain and bleeding from the vagina. Placental abruption can lead to an emergency in which a baby needs to be delivered early.

Placenta previa. This condition happens when the placenta partly or totally covers the cervix. Placenta previa is more common early in pregnancy. It might get better on its own as the uterus grows.

Placenta previa can cause serious vaginal bleeding during pregnancy or delivery. Treatment depends on various factors. They include the amount of bleeding, whether bleeding stops, how far along the pregnancy is and the placenta's position. If placenta previa continues late into the pregnancy, a healthcare professional likely will recommend a C-section.

Placenta accreta. Most often, the placenta separates from the wall of the uterus after childbirth. With placenta accreta, part or all of the placenta stays firmly attached to the uterus. This condition happens when the blood vessels and other parts of the placenta grow into the uterine wall. This can cause serious blood loss during delivery.

Sometimes, the placenta invades well into the muscles of the uterus or grows through the uterine wall. If this happens, a healthcare professional likely will recommend a C-section followed by surgery to remove the uterus. This is called a C-hysterectomy.

Without treatment, a retained placenta can cause a serious infection or life-threatening blood loss. Treatment may include medicine to help deliver the placenta or a procedure to remove the placenta.

What are symptoms of trouble with the placenta?

Call your healthcare professional if you have any of the following symptoms during pregnancy:

• Bleeding from the vagina, especially if it's heavy.
• Pain in the stomach area, also called the abdomen.
• Tightening and relaxing of the muscles in the uterus, also called uterine contractions.

What can I do to lower my risk of conditions that affect the placenta?

Most medical issues related to the placenta can't be prevented directly. But you can take steps to boost your chances for a healthy pregnancy:

• Go to all of your routine pregnancy checkups.
• Work with your healthcare professional to manage any health conditions, such as high blood pressure.
• Don't smoke or use drugs. If you need help quitting, talk with your health care professional.
• If you're thinking about getting a C-section, ask your healthcare professional about the risks.

If you had a condition that affected the placenta during a past pregnancy and you’re planning another pregnancy, talk with your healthcare professional. Ask about ways to lower the risk of getting that condition again. Also tell your healthcare professional if you've had surgery on your uterus.

How is the placenta delivered?

If you deliver your baby through your vagina, you'll also deliver the placenta that way shortly afterward. This is known as the third stage of labor.

After you give birth, you keep having mild contractions. Your healthcare professional might give you a shot of medicine called oxytocin (Pitocin). This helps you keep having contractions. It also lessens bleeding after you deliver your baby. Your healthcare professional also might massage your lower abdomen. This encourages the uterus to contract and release the placenta through the vagina. You might be asked to push to deliver the placenta.

If you have a C-section, your healthcare professional removes the placenta from your uterus during that procedure.

After it's delivered, your health care professional checks the placenta to make sure it's intact. Any pieces left behind need to be removed from the uterus to prevent bleeding and infection. If you're interested, ask to see the placenta. In some cultures, families bury the placenta in a special place.

If you have questions about the placenta during pregnancy, talk with a member of your healthcare team. Your healthcare professional can help you better understand the placenta's role in pregnancy.

There is a problem with information submitted for this request. Review/update the information highlighted below and resubmit the form.

From Mayo Clinic to your inbox

Sign up for free and stay up to date on research advancements, health tips, current health topics, and expertise on managing health. Click here for an email preview.

Error Email field is required

Error Include a valid email address

To provide you with the most relevant and helpful information, and understand which information is beneficial, we may combine your email and website usage information with other information we have about you. If you are a Mayo Clinic patient, this could include protected health information. If we combine this information with your protected health information, we will treat all of that information as protected health information and will only use or disclose that information as set forth in our notice of privacy practices. You may opt-out of email communications at any time by clicking on the unsubscribe link in the e-mail.

Thank you for subscribing!

You'll soon start receiving the latest Mayo Clinic health information you requested in your inbox.

Sorry something went wrong with your subscription

Please, try again in a couple of minutes

• Roberts V, et al. Placental development and physiology. https://www.uptodate.com/contents/search. Accessed Oct. 19, 2023.
• Lockwood CJ, et al. Placenta previa: Epidemiology, clinical features, diagnosis, morbidity and mortality. https://www.uptodate.com/contents/search. Accessed Oct. 19, 2023.
• Baggish MS, et al. Cesarean section. In: Atlas of Pelvic Anatomy and Gynecologic Surgery. 5th ed. Elsevier; 2021. https://www.clinicalkey.com. Accessed Oct. 25, 2023.
• Cunningham FG, et al., eds. Causes of obstetrical hemorrhage. In: Williams Obstetrics. 26th ed. McGraw Hill; 2022. https://accessmedicine.mhmedical.com. Accessed Oct. 19, 2023.
• Lockwood CJ, et al., eds. Placenta previa and accreta, vasa previa, subchorionic hemorrhage, and abruptio placentae. In: Creasy and Resnik's Maternal-Fetal Medicine: Principles and Practice. 9th ed. Elsevier; 2023. https://www.clinicalkey.com. Accessed Oct. 19, 2023.
• Wick MJ, ed. Managing mom's health concerns. In: Mayo Clinic Guide to a Healthy Pregnancy. 2nd ed. Mayo Clinic; 2018.
• Moore KL, et al. Placenta and fetal membranes. In: The Developing Human: Clinically Oriented Embryology. 11th ed. Elsevier; 2020. https://www.clinicalkey.com. Accessed Oct. 19, 2023.
• Martin RJ, et al., eds. Placental pathology. In: Fanaroff and Martin's Neonatal-Perinatal Medicine: Disease of the Fetus and Infant. 11th ed. Elsevier; 2020. https://www.clinicalkey.com. Accessed Oct. 19, 2023.
• Weeks A. Retained placenta after vaginal birth. https://www.uptodate.com/contents/search. Accessed Oct. 19, 2023.
• Landon MB, et al., eds. Placenta accreta spectrum. In: Gabbe's Obstetrics: Normal and Problem Pregnancies. 8th ed. Elsevier; 2021. https://www.clinicalkey.com. Accessed Oct. 19, 2023.
• FAQs: Bleeding during pregnancy. American College of Obstetricians and Gynecologists. https://www.acog.org/womens-health/faqs/bleeding-during-pregnancy. Accessed Oct. 19, 2023.
• What complications can affect the placenta? National Health Service. https://www.nhs.uk/pregnancy/labour-and-birth/what-happens/placenta-complications/. Accessed Oct. 27, 2023.

Products and Services

• Available Solutions for Prenatal Nutrition from Mayo Clinic Store
• A Book: Mayo Clinic Guide to a Healthy Pregnancy
• Air travel during pregnancy
• Allergy medications during pregnancy
• Ankle swelling during pregnancy
• Antibiotics and pregnancy
• Aspirin during pregnancy
• Pregnancy back pain
• Falling during pregnancy: Reason to worry?
• Fetal ultrasound
• Flu shot in pregnancy
• Headaches during pregnancy: What's the best treatment?
• Iron deficiency anemia during pregnancy: Prevention tips
• Leg cramps during pregnancy
• Pregnancy acne
• Pregnancy and fish
• Pregnancy constipation
• Pregnancy diet: Essential nutrients
• Pregnancy due date calculator
• Pregnancy exercises
• Pregnancy nutrition don'ts
• Pregnancy stretches
• Pregnancy weight gain
• Pregnant. Now What Happens?
• Prenatal testing
• Prenatal vitamins and pregnancy
• Sex during pregnancy
• Twin pregnancy
• Vaccines during pregnancy
• Vaping during pregnancy
• Working during pregnancy
• X-ray during pregnancy

Mayo Clinic does not endorse companies or products. Advertising revenue supports our not-for-profit mission.

• Opportunities

Mayo Clinic Press

Check out these best-sellers and special offers on books and newsletters from Mayo Clinic Press .

• Mayo Clinic on Incontinence - Mayo Clinic Press Mayo Clinic on Incontinence
• The Essential Diabetes Book - Mayo Clinic Press The Essential Diabetes Book
• Mayo Clinic on Hearing and Balance - Mayo Clinic Press Mayo Clinic on Hearing and Balance
• FREE Mayo Clinic Diet Assessment - Mayo Clinic Press FREE Mayo Clinic Diet Assessment
• Mayo Clinic Health Letter - FREE book - Mayo Clinic Press Mayo Clinic Health Letter - FREE book
• Healthy Lifestyle
• Placenta - How it works whats normal

5X Challenge

Thanks to generous benefactors, your gift today can have 5X the impact to advance AI innovation at Mayo Clinic.

pregnancy health center / pregnancy a-z list / what is a placenta article

What Is a Placenta?

• Medical Author: Dr. Sruthi M., MBBS
• Medical Reviewer: Shaziya Allarakha, MD

3 parts of the placenta

4 common types of placental placements, 4 abnormal placental attachments, 6 complications of the placenta, how does the placenta develop, what factors influence the conditions of the placenta, what are the signs of placental complications.

• Comments **COMMENTSTAGLIST**
• More **OTHERTAGLIST**

During pregnancy , a special organ develops in the uterus to support the life of the fetus ; this is known as the placenta . As the embryo implants in the uterus, some cells from the embryo transform into special structures, which eventually develop into the placenta.

One end of the placenta is attached directly to the uterus, and on the other end, it is attached to the fetus through the umbilical cord.

• The placenta is responsible to provide the fetus with oxygen, nutrients, hormones, and other essential substances through the mother’s blood.
• It is important for the survival of the fetus.
• The placenta removes metabolic waste products from the fetus.

After the baby is delivered, the placenta detaches from the uterus and is delivered. Delivery of the placenta is considered the third stage of labor .

The placenta of humans is discoid and hemochorial, which means the shape of the placenta is disc-shaped, and the fetal part of the placenta (chorion) is in direct contact with the blood of the mother.

The placenta is divided into three layers that include:

• Amnion: Amnion is the name given to the innermost placental layers that surround the fetus. Within the amniotic cavity lies the fetus immersed in the amniotic fluid . Amniotic fluid is a clear yellow liquid that allows the proper development of the fetus.
• Allantois: Allantois is the placenta's middle layer that is derived from the embryonic hindgut ( digestive system ). It eventually develops into urachus that drains fetal urine from the urinary bladder. Urachus is a cord-like structure that passes through the umbilical cord.
• Cytotrophoblast on the inner side
• Syncytiotrophoblast on the outer side

Wherever the fertilized egg implants in the uterus, the placenta attaches and develops.

The placenta can be placed in various locations; however, here are a few of the most common ones:

• Posterior placenta: The placenta develops in the back of the uterine wall, where the fertilized egg is attached.
• Anterior placenta: The placenta adheres to the front wall of the uterus, and the fetus develops behind it.
• Fundal placenta: This occurs when the placenta attaches to the upper wall of your uterus.
• Left/right lateral placenta: The placenta adheres to the left or right wall of the uterus.

Sometimes, the placenta attaches and grows in positions that cause complications during the development of the fetus or may cause complications during vaginal delivery. These abnormal positions are detected while performing routine ultrasound scans.

• Complete previa: The placenta entirely covers the cervical opening.
• Partial previa: The placenta covers some of the cervical aperture.
• Marginal previa: It occurs when the placenta spreads to the cervix's border but does not cover it.
• Placenta accreta: The placenta attaches too deeply to the uterine wall but does not penetrate the uterine muscle. This is seen in 1 out of 2,500 pregnancies.
• Placenta increta: The placenta connects to the uterine wall further deeper and penetrates the uterine muscle. Placental increta accounts for roughly 15 percent of all cases.
• Placenta percreta: The placenta enters the uterine wall and joins to another organ such as the bladder. Placenta percreta is the rarest of the three disorders and accounts for just about five percent of all occurrences.

Health News

• Brain's Wiring May Trigger Depression in Some People
• Almost 1 in 4 Adults Under 40 Have High Blood Pressure
• Saltwater Drops in Nose Could Shorten Kids' Colds
• Cuffs on At-Home Blood Pressure Monitors Don't Fit Some Patients
• Exposure to PFAS 'Forever Chemicals' in Pregnancy Could Boost Long-Term Obesity Risk

Complications related to the placenta are very rare, but when they occur, they can cause severe complications to the fetus and mother and include:

• Placenta previa: The placenta partially or completely covers the cervix, which is the entrance through which the baby will emerge. This problem is more frequent early in pregnancy and usually resolves as the placenta grows higher in the uterus. Cesarean delivery will be required if the placenta is still blocking the cervix near the time of delivery.
• Placenta accreta: The placenta develops too deeply into the uterine wall. This can result in severe blood loss during or after delivery, which can be fatal.
• Placental insufficiency: The failure of the placenta to give enough nutrition to the unborn fetus during pregnancy is referred to as placental insufficiency. This is caused by the placenta failing to grow or function properly, and it can lead to fetal growth limitation and low birth weight. Although there are no documented signs of placental insufficiency, the unborn baby may move less frequently than usual. During routine medical checkups, the healthcare provider can discover fetal growth restriction by measuring the height of the top of the uterus known as the fundus. An ultrasound scan can be used to monitor the status and size of the placenta, as well as the baby's health.
• Infarcts in the placenta: Within the placenta, there may be patches of dead tissue termed infarcts caused by diminished blood flow in specific locations. These infarcts are frequently caused by a problem with the placental vessels. Severe pregnancy-induced hypertension has been linked to an increase in the number of placental infarcts. In most cases, infarcts in the placenta do not affect the unborn child. However, in some circumstances, particularly in women with severe hypertension , the reduced blood flow in the placenta may be sufficient to cause poor growth and even death of the unborn baby.
• Placental abruption: Placental abruption is a pregnancy complication in which a portion or whole of the placenta separates from the uterus before the baby is delivered. The placenta has several blood vessels that transport nutrients from the mother to the unborn baby. When the placenta separates during pregnancy, these blood vessels rupture, resulting in bleeding. The more the bleeding, the larger the area that detaches.
• Retained placenta: If the placenta is not delivered within 30 minutes after the baby's delivery, it is said to be retained. It is a major issue because it can result in serious infection or life-threatening blood loss. Retained placenta is a rare but serious condition.

The chorion occurs about 10 days after conception as soon as the fertilized egg implants in the uterus. It is an embryonic organ that develops before the placenta.

The placenta is fully developed by week 18 to 20 of pregnancy, yet it continues to supply oxygen, nutrients, and immunity to the developing baby. By week 14 of pregnancy, the mother's blood supply is attached to the developing placenta.

The placenta is classified into two components:

• Maternal placenta: At roughly 7 to 12 days following conception, this component of the placenta develops from the mother's uterine tissue.
• Fetal placenta: When the blastocyst (the earliest form of the embryo) divides and burrows deep into the uterus to attach to the mother's blood supply, this component forms. It begins to form 17 to 22 days after conception.

The umbilical cord connects the placenta to the baby's abdomen, which is connected to the mother's uterus. The placenta is in charge of manufacturing pregnancy hormones and hosting vital nutritional exchanges between the mother's and baby's blood supplies.

The fetal blood is carried through the placenta, which is packed with maternal blood by small blood capillaries. Nutrients and oxygen are transferred from the mother's blood to the fetal blood, and waste is returned to the mother's blood—all without any mixing of the two blood sources.

Factors that influence the health of the placenta include:

• Smoking history
• High blood pressure
• Multiple pregnancies
• Maternal blood-clotting disorders
• Uterine surgery, such as Cesarean delivery, in the past
• History of placental issues
• Cocaine usage by mothers (an example of maternal substance misuse)
• Abdominal trauma such as that caused by a fall or physical assault
• Maternal age (women older than 40 years are more likely to experience placental issues)
• Preterm membrane rupture and premature amniotic sac rupture increases the risk of placental complications

If a pregnant woman develops the following symptoms, she must immediately seek medical attention because they may be caused by complications of the placenta and, if not treated in time, may lead to serious complications even death of the fetus.

• Vaginal bleeding
• Severe abdominal pain
• Excessive uterine contractions

Due to some specific complications of the placenta, vaginal delivery may not be possible or may cause serious complications. In such cases, the doctor performs a Cesarean delivery rather than normal vaginal delivery.

Subscribe to MedicineNet's Pregnancy & Newborns Newsletter

By clicking "Submit," I agree to the MedicineNet Terms and Conditions and Privacy Policy . I also agree to receive emails from MedicineNet and I understand that I may opt out of MedicineNet subscriptions at any time.

Top What Is a Placenta Related Articles

Can a Baby Survive Placental Abruption?

Pregnancy Discomforts: Common Causes

16 Early Signs & Symptoms of Pregnancy: Could You Be Pregnant?

Am I Pregnant Quiz

Embryo vs. Fetus: Differences Between Stages Week by Week

How Do You Fix a Prolapsed Uterus?

How do you know if you have a prolapsed uterus.

Is Cervical Stitch Safe During Pregnancy?

Pregnancy: Multiple Births, Twins, Triplets, and More

Pregnancy Myths and Facts Quiz

Pregnancy Planning (Tips)

Placenta Previa

What Foods Should I Eat During My First Trimester of Pregnancy?

Stages of Pregnancy: Week by Week

Pregnancy: 7 Common Third Trimester Tests

Tubal Pregnancy Picture

JOSEPH F. YETTER, III, COL, MC, USA

Am Fam Physician. 1998;57(5):1045-1054

A one-minute examination of the placenta performed in the delivery room provides information that may be important to the care of both mother and infant. The findings of this assessment should be documented in the delivery records. During the examination, the size, shape, consistency and completeness of the placenta should be determined, and the presence of accessory lobes, placental infarcts, hemorrhage, tumors and nodules should be noted. The umbilical cord should be assessed for length, insertion, number of vessels, thromboses, knots and the presence of Wharton's jelly. The color, luster and odor of the fetal membranes should be evaluated, and the membranes should be examined for the presence of large (velamentous) vessels. Tissue may be retained because of abnormal lobation of the placenta or because of placenta accreta, placenta increta or placenta percreta. Numerous common and uncommon findings of the placenta, umbilical cord and membranes are associated with abnormal fetal development and perinatal morbidity. The placenta should be submitted for pathologic evaluation if an abnormality is detected or certain indications are present.

Examination of the placenta can yield information that may be important in the immediate and later management of mother and infant. This information may also be essential for protecting the attending physician in the event of an adverse maternal or fetal outcome.

Although some experts argue that all placentas should be examined by a pathologist, 1 most hospitals do not mandate this examination. Instead, the delivering physician is usually responsible for determining when pathologic interpretation is necessary. In some urgent situations, decisions must be made before pathologic interpretation is available or has been completed. Therefore, it is essential that the delivering physician perform a thorough, accurate examination of the placenta.

The examination of normal placentas and most abnormal placentas can be accomplished within one minute. Universal examination of the placenta in the delivery room, with documentation of findings and submission of tissue for pathologic evaluation based on abnormal appearance or certain clinical indications, is standard medical practice. 3 (pp701–3)

Clinical Characteristics of the Normal Placenta

The usual term placenta is about 22 cm in diameter and 2.0 to 2.5 cm thick. It generally weighs approximately 470 g (about 1 lb). However, the measurements can vary considerably, and placentas generally are not weighed in the delivery room.

The maternal surface of the placenta should be dark maroon in color and should be divided into lobules or cotyledons. The structure should appear complete, with no missing cotyledons. The fetal surface of the placenta should be shiny, gray and translucent enough that the color of the underlying maroon villous tissue may be seen.

At term, the typical umbilical cord is 55 to 60 cm in length, 3 with a diameter of 2.0 to 2.5 cm. The structure should have abundant Wharton's jelly, and no true knots or thromboses should be present. The total cord length should be estimated in the delivery room, since the delivering physician has access to both the placental and fetal ends.

The normal cord contains two arteries and one vein. During the placental examination, the delivering physician should count the vessels in either the middle third of the cord or the fetal third of the cord, because the arteries are sometimes fused near the placenta and are therefore difficult to differentiate.

Fetal membranes are usually gray, wrinkled, shiny and translucent. The membranes and the placenta have a distinctive metallic odor that is difficult to describe but is easily recognized with experience. Normally, the placenta and the fetal membranes are not malodorous.

Potential Abnormalities of the Placenta

The placental abnormalities that may be detected in the delivery room are discussed in the following sections. Photographs of a number of these abnormalities are presented ( Figures 1 through 6 ) . The examination of the placenta and the significance of clinical findings are summarized in Table 1 . 3 – 11

Placental Completeness

Evaluating placental completeness is of critical, immediate importance in the delivery room. Retained placental tissue is associated with postpartum hemorrhage and infection.

The maternal surface of the placenta should be inspected to be certain that all cotyledons are present. Then the fetal membranes should be inspected past the edges of the placenta. Large vessels beyond these edges indicate the possibility that an entire placental lobe (e.g., succenturiate or accessory lobe) may have been retained ( Figure 1 ) .

All or part of the placenta is retained in placenta accreta, placenta increta and placenta percreta. In these conditions, the placental tissues grow into the myometrium to lesser or greater depths. Manual exploration and the removal of retained placental tissue are necessary in these cases.

Placental Size

Placentas less than 2.5 cm thick are associated with intrauterine growth retardation of the fetus. 4 Placentas more than 4 cm thick have an association with maternal diabetes mellitus, fetal hydrops (of both immune and nonimmune etiology) and intrauterine fetal infections. 5 (pp423–36,476,542–613)

An extremely thin placenta may represent placenta membranacea. In this condition, the entire uterine cavity is lined with thin placenta. Placenta membranacea is associated with a very poor fetal outcome.

Placental Shape

Extra placental lobes are important, primarily because they may lead to retained placental tissue ( Figure 2 ) .

Blood may be adherent to the maternal surface of the placenta, particularly at or near the margin. If the blood is rather firmly attached, and especially if it distorts the placenta, it may represent an abruption. The dimensions and volume of the placenta should be estimated.

Placental Consistency and Surfaces

The placenta should be palpated, and the fetal and maternal surfaces should be carefully examined.

Maternal Surface . In a term infant without anemia, the maternal surface of the placenta should be dark maroon. In a premature infant, the placenta is lighter in color. Pallor of the maternal surface indicates the presence of fetal anemia, which may be a sign of hemorrhage. With prompt recognition of fetal hemorrhage (such as occurs in vasa previa), lifesaving transfusion can be performed.

Clots on the maternal surface, particularly adherent centrally located clots, may represent placental abruption. It should be emphasized, however, that abruption is a clinical diagnosis.

Fetal Surface . A thick ring of membranes on the fetal surface of the placenta may represent a circumvallate placenta ( Figure 3 ) , which is associated with prematurity, prenatal bleeding, abruption, multiparity and early fluid loss. 5 (pp386–91) A similar but thinner ring of membrane tissue represents a circummarginate placenta ( Figure 4 ) . A circummarginate placenta is probably of no clinical significance, although one study found an association between this structural anomaly and an increase in fetal malformations. 5 (pp386–91)

Numerous small, firm, white, gray or yellow nodules on the fetal surface may represent either amnion nodosum ( Figure 5 ) or squamous metaplasia. Amnion nodosum is associated with oligohydramnios, renal agenesis and poor fetal outcome. Squamous metaplasia is common and is probably of no fetal significance.

A nodule or thickening on the fetal surface may represent a vanished twin or a fetus papyraceus. A deceased twin sometimes coexists with a normal fetus, but it may also be associated with demise of the second twin, and this second death may be of uncertain cause. 5 (pp684–70)

Delicate or more robust bands of amnionic tissue may strangle and amputate fetal parts, including digits, entire limbs, head, neck or trunk. In such cases, amnion may be missing from the placenta but present on the cord. 5 (pp162–8) When fetal parts are missing or amputated, careful pathologic examination of the placenta is warranted.

Placental Parenchyma

A diffusely soft placenta may represent infection, particularly if the structure is also thickened. Firm areas in the placenta may represent fibrin deposition or infarction. Fresh infarcts are red, while older infarcts are gray. Fibrin deposits are gray and, if extensive, may be associated with intrauterine growth retardation and other poor fetal outcomes. If infarcts or fibrin occupy less than 5 percent of the placental mass, they are usually unimportant.

Focal fleshy, dark-red areas may represent chorioangiomas. 5 (pp423–36) These benign hemangiomas occur in 1 percent of placentas. While small chorioangiomas are usually of no clinical significance, large chorioangiomas are associated with fetal anemia, thrombocytopenia, hydrops, hydramnios, intrauterine growth retardation, prematurity and stillbirth. 5 (pp841–6)

Gestational trophoblastic neoplasia, including benign hydatidiform moles, invasive moles and choriocarcinoma, only rarely coexist with viable gestations. Moles appear as grape-like clusters of edematous villi, while choriocarcinoma may look much like an infarct. 6

Apparent hemorrhage deep to the fetal membranes or a dark-colored cyst may represent Breus' mole, which is associated with Turner's syndrome (45, X) and with fetal demise. 5 (pp293–6)

Any suspicious specimen must be examined by a pathologist, with follow-up as indicated by the disease process.

Umbilical Cord

While opinions of authorities differ with regard to the limits of normal for cord length, 40 to 70 cm would appear to be a reasonable range. 3 , 5 (pp183–5) , 7 The typical umbilical cord is long enough (55 to 60 cm) to allow the infant to begin nursing before placental delivery. This provides a release of oxytocin to facilitate uterine contractions and both the shearing and delivery of the placenta. 3

In part, cord length is genetically determined. However, the length of the umbilical cord is also increased by the tension the fetus places on the cord. Hence, a short cord is associated with a less active fetus, fetal malformations, myopathic and neuropathic diseases, Down syndrome and oligohydramnios.

Short cords may result in cord rupture, hemorrhage and stricture. Cords of insufficient length may also result in breech and other fetal malpresentations, a prolonged second stage of labor, abruption and uterine inversion. 3

The umbilical cord may become excessively long because of fetal hyperkinesis. Long cords are associated with entanglements, torsion, knots and thromboses.

Abnormalities of cord length are clearly associated with an array of longstanding intrauterine factors and consequences, some of which may become apparent only much later in a child's life. Hence, cord length should be documented for every delivery.

Cord Diameter and Inflammation

Throughout its length, the typical umbilical cord has a fairly uniform diameter (2.0 to 2.5 cm). Narrow areas may represent a focal deficiency of Wharton's jelly and are associated with torsion and fetal death. 3

Diffuse edema of the cord is associated with hemolytic disease, prematurity, cesarean section, maternal preeclampsia, eclampsia and diabetes mellitus. Cord edema may also be associated with either transient tachypnea of the newborn or idiopathic respiratory distress syndrome. Focally edematous cords are associated with trisomy 18 syndrome, patent urachus and omphalocele.

Necrotizing funisitis is a severe inflammation of the cord that sometimes has a distinctive segmental resemblance to a barber's pole. 8 This inflammatory condition may represent syphilis or some other acute, subacute or chronic infection. Swelling, necrosis, thrombosis and calcifications may be present. 5 (pp278–80)

Cord Insertion

The umbilical cord typically inserts into the placenta near its center. About 90 percent of cord insertions are central or eccentric. About 7 percent of umbilical insertions occur at the placental margin. Marginal insertions are generally benign.

In about 1 percent of singleton fetuses, cord insertion is velamentous ( Figure 6 ) . This type of cord insertion is associated with an increased risk of fetal hemorrhage from the unprotected vessels, as well as vascular compression and thrombosis. Velamentous cord insertion is also associated with advanced maternal age, diabetes mellitus, smoking, a single umbilical artery and fetal malformations.

Webs of amnion at the base of the cord may compromise circulation to the fetus.

A true cord knot occurs when the fetus passes through a loop of umbilical cord, usually early in pregnancy. In most cases, a knot does not cause fetal compromise. However, if sufficient tension is placed on the cord before or during labor and delivery, blood flow may be cut off, and signs of fetal asphyxia may occur.

Cord Vessels

The umbilical cord typically contains two arteries and a single vein. If only one artery and one vein are grossly visible, the fetal anomaly rate is nearly 50 percent. 11 These anomalies may affect the cardiovascular, genitourinary or gastrointestinal system, and other systems as well. 5 (pp183–5), 9

Thrombosis of cord vessels is often overlooked by both delivering physicians and pathologists. This is an important cause of fetal injury. 10

Free Fetal Membranes

Fetal membranes should be thin, gray and glistening. Thick, dull, discolored or foul-smelling membranes indicate the possibility of infection. The nature of the odor may provide a clue to the infecting organism: a fecal odor may indicate Fusobacterium or Bacteroides, while a sweet odor may indicate Clostridium or Listeria. 5 (pp542)

Green-colored fetal membranes are frequently the result of meconium staining. However, a green color may be imparted by changing blood pigments from an earlier bleeding event or by the myeloperoxidase in leukocytes in the case of infection.

Thick green slime that easily rinses off the membranes is meconium. Any other pigmentation requires histologic determination.

Pathologic Examination of the Placenta

When any abnormality of potential clinical significance is identified, the placenta should be sent for pathologic examination. Cultures or additional special studies should be obtained before the placenta is sent to pathology.

Indications for pathologic examination include a poor pregnancy outcome (prematurity, intrauterine growth retardation, perinatal death and asphyxia), systemic maternal disorders, third-trimester bleeding and evidence of fetal or maternal infection. 2 (pp701–3)

In patients with multiple gestations, the placenta must be examined for zygosity, vascular anastomoses and numerous common abnormalities. The individual cords should be labeled for the pathologist (i.e., twin A and twin B).

Controversy exists as to whether the placental specimen should be fixed in formalin or refrigerated. Therefore, the guidelines of the delivering physician's institution should be followed. If the specimen is to be fixed, copious amounts of formalin (at least 10 times as much formalin as placental tissue) should be used. Refrigerating the specimen in a container the size of a large ice cream carton preserves the placenta very well for a few days and allows it to be available if the infant shows some abnormal clinical findings during the first few days of life.

The pathologist should be notified of the clinical situation, and questions should be answered. Interest in placental pathology has increased in recent years, and the pathologist can contribute to the diagnosis and treatment of the mother and infant. 2 (pp660–721)

Ultrasonography and Fetal Surgery

Ultrasonography can be used to identify many of the abnormalities described in this article. Indeed, ultrasonography and the possibility of surgical intervention have been partly responsible for the resurgence of interest in placental pathology. Discussions of ultrasound examination and fetal surgery, as well as the development of the placenta, are beyond the intended scope of this article. However, an excellent review article on placental ultrasonography is available. 4

Final Comment

Pathology fees for placental examination vary but are similar to those for a surgical specimen. The question of whether pathologic examination of the placenta will change outcome must be considered.

Documentation of the delivery room examination of the placenta, plus the pathologic examination when indicated clinically or by hospital policy, will preserve valuable information. 12 A suggested form for documenting the clinical findings and the indications for pathologic evaluation is presented in Figure 7 . Since some indications for placental examination are not apparent at the time of delivery, it may be wise to save the placenta (labeled and refrigerated or preserved in formalin) until the neonatal outcome is determined.

It has been suggested that all placentas should be sent for complete pathologic examination, 7 but this approach may represent an overuse of resources. In any event, if placentas are sent to pathology for the indications that have been discussed in this article, few necessary examinations are likely to be missed. 1 At minimum, the hospital's requirements for the handling of placentas should be followed.

Salafia CM, Vintzileos AM. Why all placentas should be examined by a pathologist in 1990. Am J Obstet Gynecol. 1990;163(4 Pt 1):1282-93.

College of American Pathologists. Conference XIX on the Examination of the Placenta: report of the Working Group on Indications for Placental Examination. Arch Pathol Lab Med. 1991;115:660-721.

Heifetz SA. The umbilical cord: obstetrically important lesions. Clin Obstet Gynecol. 1996;39:571-87.

Kuhlmann RS, Warsof S. Ultrasound of the placenta. Clin Obstet Gynecol. 1996;39:519-34.

Benirschke K, Kaufmann P. Pathology of the human placenta. 2d ed. New York: Springer-Verlag, 1990.

Driscoll SG. Choriocarcinoma: “incidental finding” within a term placenta. Obstet Gynecol. 1963;21:96-101.

Kaplan CG. Postpartum examination of the placenta. Clin Obstet Gynecol. 1996;39:535-48.

Fojaco RM, Hensley GT, Moskowitz L. Congenital syphilis and necrotizing funisitis. JAMA. 1989;261:1788-90.

Macpherson T. Fact and fancy. What can we really tell from the placenta?. Arch Pathol Lab Med. 1991;115:672-81 1991;115:1211]

Rayne SC, Kraus FT. Placental thrombi and other vascular lesions. Classification, morphology, and clinical correlations. Pathol Res Pract. 1993;189:2-17.

Leung AK, Robson WL. Single umbilical artery. A report of 159 cases. Am J Dis Child. 1989;143:108-11.

Kaplan CG. Forensic aspects of the placenta. Perspect Pediatr Pathol. 1995;19:20-42.

Continue Reading

More in afp, more in pubmed.

Copyright © 1998 by the American Academy of Family Physicians.

This content is owned by the AAFP. A person viewing it online may make one printout of the material and may use that printout only for his or her personal, non-commercial reference. This material may not otherwise be downloaded, copied, printed, stored, transmitted or reproduced in any medium, whether now known or later invented, except as authorized in writing by the AAFP.  See permissions  for copyright questions and/or permission requests.

Copyright © 2024 American Academy of Family Physicians. All Rights Reserved.

• Tracking cycle
• Getting pregnant
• Help Center
• Flo for Partners
• Anonymous Mode
• Flo app reviews
• Flo Premium New
• Secret Chats New
• Symptom Checker New
• Health 360°
• Being a mom
• Ovulation calculator
• hCG calculator
• Pregnancy test calculator
• Period calculator
• Implantation calculator
• Pregnancy calculator
• Pregnancy due date calculator
• IVF and FET due date calculator
• Due date calculator by ultrasound
• Medical Affairs
• Science & Research
• Pass It On Project New
• Privacy Portal
• Press Center

Posterior Placenta Location: Is Posterior Positioning Good for the Baby?

Every piece of content at Flo Health adheres to the highest editorial standards for language, style, and medical accuracy. To learn what we do to deliver the best health and lifestyle insights to you, check out our content review principles .

When you become pregnant, your body begins to adjust to the fetus and undergoes many changes. One of these changes is the growth of the placenta in your uterus.

The placenta is a temporary organ that attaches itself to the uterus and to the fetus’s umbilical cord. It’s through the placenta that the growing fetus is able to get oxygen and nutrients.

The positioning of the placenta is very important and determines whether you will be able to give birth vaginally or if a cesarean section  will be safer. 

Placental development stages

By attaching itself to the fetus’s umbilical cord, the placenta provides the fetus with nourishment and oxygen while also eliminating the fetus’s waste. 

How does the placenta develop?

The placenta begins to grow when the blastocyst implants itself into your uterus. The blastocyst is the bunch of cells, referred to as the inner cell mass, that develops into the embryo. The outer cluster of cells, known as the trophoblast , forms the placenta. 

The trophoblast grows quickly, and its cells split into two layers: cytotrophoblasts , which are the inner cells, and syncytiotrophoblasts , which are the outer cells. 

The inner cells of the placenta reshape blood vessels in your uterus. This is how the placenta receives blood to provide the fetus with nutrients. 

The placenta develops wherever the fertilized egg embeds itself in your uterus: 

• Anterior position — on the front wall of your uterus, closest to the belly
• Posterior position — on the back wall of your uterus, closest to the spine
• Fundal position — on the top wall of your uterus
• Lateral position — on the right or left side of your uterus

These are all normal places for the placenta to implant and grow.

When the placenta attaches itself to the back of the uterus, it is called a posterior placenta. When it attaches itself to the front of the uterus, it is known as an anterior placenta. 

The placenta undergoes numerous changes from conception to birth. As the fetus grows, the placenta grows to accommodate their development. By the time you give birth, the placenta may weigh as much as a pound (500 grams) and measure 9 inches in length. After the baby is born, your uterus will also contract to expel the placenta. 

Take a quiz

Find out what you can do with our Health Assistant

What is it?

The term posterior placenta describes the placenta’s attachment to the back wall of the uterus. 

If your health care provider determines that you have a posterior placenta, there’s no need to worry. It’s completely normal. The upper (or fundal) portion of the uterine back wall is one of the best locations for the fetus to be in. It allows them to move into the anterior position just before birth.

Furthermore, a posterior placenta does not affect or interfere with the growth and development of the fetus.

How does placenta positioning affect delivery?

During pregnancy, the placenta location can change. This is why your health care provider may perform an ultrasound scan in the second trimester of pregnancy (roughly 18 to 21 weeks). Another scan may be necessary in the third trimester to double-check placenta positioning before delivery.

One placental location that might be problematic is when the placenta grows toward the cervix. This is called placenta previa. In this position, the placenta could detach from the uterine wall and cause premature labor or internal bleeding. 

Another condition, known as placenta accreta, happens when parts of the placenta attach too deeply into the uterine wall. Instead of completely detaching itself after delivery, some or all of the placenta remains in the uterus, sometimes resulting in bleeding.  

In such cases, your health care provider may recommend a caesarian section and a post-delivery hysterectomy. 

In some rare instances, the placenta remains in the uterus after the baby has been delivered. This is called a retained placenta , and when left untreated, it can lead to complications including infections and heavy vaginal bleeding.  

Anterior vs. posterior placenta

To recap, a posterior placenta is one that attaches itself to the back of the uterus, while an anterior placenta attaches itself to the front. Both placental positions are considered normal. Aside from being an ideal location for delivery, the other benefit of a posterior placenta is being able to feel your baby’s movements early on. 

This is not the case with an anterior placenta because the placenta may create more space between the baby and your abdomen. Neither posterior or anterior placental location will affect the development or growth of a strong and healthy baby.

Zia, Shumaila. “Placental Location and Pregnancy Outcome.” Journal of the Turkish German Gynecological Association, AVES, 1 Dec. 2013, www.ncbi.nlm.nih.gov/pmc/articles/PMC3935544/ . Mayo Clinic Staff. “Know the Role the Placenta Plays in Pregnancy.” Mayo Clinic, Mayo Foundation for Medical Education and Research, 25 Mar. 2020, www.mayoclinic.org/healthy-lifestyle/pregnancy-week-by-week/in-depth/placenta/art-20044425 . Wang, Yuping. “Cell Types of the Placenta.” Vascular Biology of the Placenta., U.S. National Library of Medicine, 1 Jan. 1970, www.ncbi.nlm.nih.gov/books/NBK53245/ . Weeks, Andrew. “Retained Placenta after Vaginal Birth.” UpToDate, 7 Apr. 2020, www.uptodate.com/contents/retained-placenta-after-vaginal-birth .

History of updates

Current version (18 july 2022), published (17 april 2019), in this article, related articles.

Understand what your symptoms might mean — and what's normal for you — by tracking your cycle.

Follow your baby's growth and see how your body is changing.

Know when you're most fertile to maximize your chances of getting pregnant.

• Success stories
• Spine and back
• Pelvis and perineum
• Head and neck
• Neuroanatomy
• Cross sections
• Radiological anatomy
• Types of tissues
• Body systems

Register now and grab your free ultimate anatomy study guide!

Author: Sara Ferreira, MD • Reviewer: Roberto Grujičić, MD Last reviewed: October 26, 2023 Reading time: 8 minutes

The placenta is a temporary organ of pregnancy situated in the uterus. It is formed from fetal and maternal components. The fetal portion is formed by the chorion frondosum , while the maternal portion is formed by the decidua basalis . Moreover, the placenta is the meeting point of two circulatory systems: fetal circulation and maternal circulation.

The main function of the placenta is the interchange between the mother and the fetus. More specifically, it provides nutrition and oxygen to the fetus and removes waste material and carbon dioxide.  

In this article, we will explore the anatomy and function of the placenta.

Gross anatomy

Fetal surface of the placenta, maternal surface of the placenta, anatomical variations, placenta disorders.

The placenta is a discoid-shaped organ weighing about 450-500g at full term. The placental thickness is usually proportional to the gestational age. The placenta is normally located along the anterior or posterior wall of the uterus and may expand to the lateral wall with the course of the pregnancy.

The placenta is composed of two different surfaces, the fetal surface (or chorionic plate) and the maternal surface (or basal plate).

The fetal surface of the placenta (or chorionic plate) is covered by the amnion , or amniotic membrane, which gives this surface a shiny appearance. The amniotic membrane secretes amniotic fluid which serves as a protection and cushion for the fetus, while also facilitating exchanges between the mother and fetus.

Underlying the amnion is the chorion , a thicker membrane continuous with the lining of the uterine wall. The chorion contains the chorionic vessels which are continuous with the vessels of the umbilical cord. Originally, early in the development of the placenta, the entire chorionic plate is covered with chorionic villi. The villi located adjacent to the decidua capsularis (portion of the decidua that overlies the embryo) degenerate to produce the smooth (nonvillous) chorion laeve . The villi adjacent to the decidua basalis persist, increase in size and produce the chorion frondosum or fetal portion of the placenta. The chorionic villi of the fully developed placenta contain a network of fetal capillaries, allowing a maximal contact area with the maternal blood. The exchanges between the fetal and maternal circulation occurs in the intervillous space . 

The umbilical cord , which is the connection between the placenta and the fetus, inserts in a slightly eccentric position into the chorionic plate. The umbilical cord contains one vein (the umbilical vein ) that carries nutrients and oxygen from the placenta to the fetus and two arteries (the umbilical arteries ) that carry waste products from the fetus back to the placenta.

The maternal surface of the placenta, or basal plate , is an artificial surface, which emerges from the separation of the placenta from the uterine wall during delivery. This surface is composed of the decidua , the modified or specialized endometrium (or mucosal lining of the uterus) that forms in preparation for pregnancy. The decidua has several parts:

• Decidua basalis - forms the portion of placenta;
• Decidua capsularis - overlies the embryo;
• Parietal decidua  - the rest of the decidual tissue. 

Also visible on the maternal surface of the placenta are slightly elevated regions called lobes or cotyledons (approximately 10 to 40), which are separated by grooves or sulci. Inside the placenta, the grooves correspond to the placental septa. Each lobe visible on the maternal surface corresponds to the position of the vilous trees arising from the chorionic plate.

This quiz helps you identify the structures of the placenta.

The placenta is a highly-specialized organ that plays an essential role during pregnancy. It is responsible for providing nutrition and oxygen to the fetus as well as removing waste material and carbon dioxide. It is also responsible for creating a separation between the maternal and fetal circulation (known as placental barrier ). Besides that, the placenta protects the fetus from infections and other maternal disorders, while also helping in the development of the fetal immune system. Additionally, this organ has an endocrine function as it secretes hormones (such as human chorionic gonadotropin) that affect the pregnancy, metabolism, fetal growth, and parturition.

Clinical notes

Variant morphologies of the placenta are frequently encountered, such as is the case of a bilobed placenta where this organ is separated into two near equal-sized lobes. The estimated incidence of this specific variation is at up to ~4% of pregnancies. It can be associated with some complications such as first-trimester bleeding.

Besides the developmental abnormalities referred above, the placenta may also be affected by a number of medical conditions. An example of these disorders is a condition known as  placenta previa , which is the implantation of the placenta over the cervical os. This condition usually presents as painless vaginal bleeding in the third trimester. In these cases, mother and fetus need careful monitoring and delivery is often by cesarean section.

Huppertz B. The anatomy of the normal placenta. J Clin Pathol. 2008 Dec;61(12):1296-302. doi: 10.1136/jcp.2008.055277. Epub 2008 Aug 28. PMID: 18755720

Kapila V, Chaudhry K. Physiology, Placenta. [Updated 2021 Jul 26]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK538332/

Herrick EJ, Bordoni B. Embryology, Placenta. [Updated 2021 May 8]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK551634/

Fadl S, Moshiri M, Fligner C, Katz D, Dighe M. Placental Imaging: Normal Appearance with Review of Pathologic Findings. Radiographics. 2017;37(3):979-98. doi:10.1148/rg.2017160155 - Pubmed

Placenta: want to learn more about it?

Our engaging videos, interactive quizzes, in-depth articles and HD atlas are here to get you top results faster.

What do you prefer to learn with?

“I would honestly say that Kenhub cut my study time in half.” – Read more.

Learning anatomy isn't impossible. We're here to help.

Learning anatomy is a massive undertaking, and we're here to help you pass with flying colours.

Want access to this video?

• Curated learning paths created by our anatomy experts
• 1000s of high quality anatomy illustrations and articles
• Free 60 minute trial of Kenhub Premium!

...it takes less than 60 seconds!

Want access to this quiz?

Want access to this gallery.

• Type 2 Diabetes
• Heart Disease
• Digestive Health
• Multiple Sclerosis
• Diet & Nutrition
• Health Insurance
• Public Health
• Patient Rights
• Caregivers & Loved Ones
• End of Life Concerns
• Health News
• Thyroid Test Analyzer
• Doctor Discussion Guides
• Hemoglobin A1c Test Analyzer
• Lipid Test Analyzer
• Complete Blood Count (CBC) Analyzer
• What to Buy
• Editorial Process
• Meet Our Medical Expert Board

The Anatomy of the Placenta

The placenta ensures fetuses get necessary food and oxygen during pregnancy.

Associated Conditions

The placenta develops within the uterus during pregnancy, playing a key role in nourishing and providing oxygen to the fetus, as well as removing waste material. This organ is attached to the wall of the uterus, with the baby’s umbilical cord arising from it. Throughout the course of a pregnancy, the placenta grows and changes shape, with its thickness being a reliable measure of how far along the mother-to-be is in gestation. Furthermore, a number of disorders can impact this organ, including placenta previa, in which some or all of the cervix is covered by the placenta, as well as placenta accreta malformations, which involve different degrees of implantation within the uterine wall.

Structure and Location

The largest fetal organ, the placenta undergoes rapid development over the course of pregnancy. By the time the baby is brought to term, it has a flat, round disc-like shape that is about 22 centimeters (cm) in diameter, with walls that are typically between 2 and 2.5 cm.

The placenta typically sits along the back wall of the uterine wall—about 6 cm from the cervix—occasionally accessing the side walls throughout its course of development. Significantly, the umbilical cord (which brings in nutrients and oxygen and takes out waste material) connects the mid-section of the fetus to the placenta; in turn, the fetus is surrounded by the amniotic or gestational sac.

The placenta undergoes consistent change throughout the course of pregnancy; between week 0 and 13 after conception, the fertilized blastocyst (what the embryo becomes once its cells start differentiating at about five days after the egg is fertilized) embeds itself in the mucous membrane (endometrium) of the uterine wall, allowing for the fetus and placenta to start forming. By the fourth or fifth month of pregnancy, the placenta takes up about half of the uterine surface, though this percentage shrinks as the fetus grows. At birth, the placenta is also ejected from the body.

Crucial to placenta (and, by extension, embryonic) development is the formation of small, finger-like structures called chorionic villi, which are composed of two types of cells—cytotrophoblasts and syncytiotrophoblasts. The former of these interact with arteries and veins in the walls of the uterus to ensure the fetus gets the nutrients and oxygen it needs. Throughout pregnancy, this vasculature grows in size and complexity, allowing for the formation of the following two major components.

• Maternal component: Essentially, this is the portion of the placenta that is formed of the mother’s endometrium or the maternal uterine tissue. It forms what is called the decidua basalis, or maternal placenta.
• Fetal component: Also known as the chorion frondosum or villous chorion, this is the portion of the placenta arising from the blastocyte.

These are held together by outgrowths, called anchoring villi, from the maternal component. The placenta is surrounded by a placental membrane or barrier. While it serves to differentiate blood supply for mother and fetus, many substances can still get through.

Anatomical Variations

Not every placenta forms regularly, and this can have serious implications. Several such malformations, including placenta previa, accreta, increta, and percreta, are considered serious medical conditions that can endanger a mother, the fetus, or both. In addition, there are a number of other commonly identified abnormalities.  

• Bilobed placenta: Also known as “placenta duplex,” this is a case where the placenta is composed of two roughly equal-sized lobes. The umbilical cord may insert into either lobe, run through both, or sit between them. Though this condition doesn’t increase risk of damage to the fetus, it can cause first-trimester bleeding, excessive amniotic fluid within the gestational sac, abruption (premature separation of the placenta from the womb), or retained placenta (when the placenta remains in the body after birth). This condition is seen in 2% to 8% of women. 
• Succenturiate placenta: In these cases, a lobe of placenta forms separately from a main body that is linked via the umbilical cord to the fetus. Essentially, it’s a variation of a bilobed placenta that occurs more commonly in women who are of advanced maternal age or in those who have had in vitro fertilization. Seen about 5% of the time, this condition can also lead to retained placenta as well as placenta previa, among other complications. 
• Circumvallate placenta: This is when the membranes of the placenta tuck back around its edges to form a ring-like (annular) shape. In this case, the outer membrane, known as the chorion causes a hematoma (a collection of blood) at the margin of the placenta, and vessels within its ring stop abruptly. This condition can lead to poor outcomes for the pregnancy due to the risk of vaginal bleeding during the first trimester, potential rupture of the membranes, pre-term delivery, insufficient development of the placenta, as well as abruption. This condition isn’t easily diagnosed during pregnancy.  
• Circummarginate placenta: This is a much less problematic variant of the above, in which the membranes do not curl back.
• Placenta membranacea: In this rare condition, chorionic villi cover the fetal membrane partially or completely, causing the placenta to develop as a thinner structure at the periphery of the membrane that encloses the chorion. This then leads to vaginal bleeding in the second and/or third trimester of pregnancy and may lead to placenta previa or accreta. 
• Ring-shaped placenta: A variation of placenta membranacea, this condition causes the placenta to have either a ring-like or horseshoe-like shape. Occurring in only about 1 in 6,000 pregnancies, this leads to bleeding before or after delivery, as well as reduced growth of the fetus.
• Placenta fenestrata: This condition is characterized by the absence of the central portion of the placenta. Also very rare, the primary concern for doctors is retained placenta at delivery.
• Battledore placenta: Sometimes called “marginal cord insertion,” this is when the umbilical cord runs through the margin of the placenta rather than the center. This occurs in between 7% and 9% of single pregnancies, but is much more common when there are twins, happening between 24% and 33% of the time. This can lead to early (preterm) labor and problems with the fetus, as well as low birth weight.

The placenta plays an absolutely crucial and essential role during the nine months of pregnancy. Via the umbilical cord and the chorionic villi, this organ delivers blood, nutrients, and oxygen to the developing fetus. In addition, it works to remove waste materials and carbon dioxide. As it does so, it creates a differentiation between maternal and fetal blood supply, keeping these separate via its membrane.

Furthermore, the placenta works to protect the fetus from certain diseases and bacterial infections and helps with the development of the baby’s immune system. This organ also secretes hormones—such as human chorionic gonadotropin, human placenta lactogen, and estrogen—necessary to influence the course of pregnancy and fetal growth and metabolism, as well as labor itself.

Aside from the developmental abnormalities listed above, the placenta may also be subject to a number of medical conditions that may be of concern to doctors. Oftentimes, the core of the problem has to do with the position of this organ. Among these are the following.

• Placenta previa : This condition occurs when the placenta forms partially or totally toward the lower end of the uterus, including the cervix, rather than closer to its upper part. In cases of complete previa, the internal os —that is, the opening from the uterus to the vagina —is completely covered by the placenta. Occurring in about 1 in 200 to 250 pregnancies, risk factors for placenta previa include a history of smoking, prior cesarean delivery, abortion, other surgery of the uterus, and older maternal age, among others. Depending on the case, cesarean delivery may be required.   
• Placenta accreta : When the placenta develops too deep within the uterine wall without penetrating the uterine muscle (myometrium), the third trimester of the pregnancy can be impacted. A relatively rare occurrence—this is the case in only 1 in every 2,500 pregnancies—this condition is more likely to occur among smokers and those with older maternal age, as well as those with a history of previous surgeries or cesarean deliveries. This also can happen alongside placenta previa. During delivery, this condition can lead to serious complications, including hemorrhage and shock. While hysterectomy —the removal of a woman’s uterus—has been the traditional treatment approach, other, more conservative options are available.     
• Placenta increta: Representing 15% to 17% of placenta accreta cases, this form of the condition is when development of the placenta is within the uterine wall and it penetrates the myometrium. Childbirth is severely impacted in these cases, since this can lead to severe hemorrhage due to retention of the placenta within the body. As such, cesarean delivery is required alongside hysterectomy or comparable treatment.   
• Placenta percreta: Yet another type of accreta, placenta percreta occurs when this organ develops all the way through the uterine wall. It may even start to grow into surrounding organs, such as the bladder or colon. Occurring in 5% of placenta accreta cases, as with placenta increta, cesarean delivery and hysterectomy is necessary in these cases.
• Placental insufficiency : Arising for a range of reasons, this is when the placenta is unable to provide enough nourishment for the fetus. This can be due to genetic defects, deficiencies of vitamins C and E, chronic infections (such as malaria), high blood pressure, diabetes, anemia, or heart disease, as well as other health issues. Treatment can range from ensuring better diet to taking medications like low-dose aspirin.

Throughout the course of pregnancy, doctors will perform a wide range of tests to ensure the health of the fetus. This can mean everything from blood tests to genetic tests are administered. When it comes to ensuring proper development of the placenta, a number of diagnostic techniques are employed, including the following.

• Ultrasound : A frequently employed approach when it comes to monitoring fetal development as well as the health of the placenta, ultrasound employs high-frequency sound waves to create a real-time video of the uterus and surrounding regions. Especially in the second and third trimesters, this approach can be used for cases of placenta previa, among other disorders. Furthermore, based on ultrasound results, doctors classify placental maturity. This system of placental grading ranges from grade 0 for pregnancy at 18 or less weeks to grade III for when things have progressed beyond week 39. Early onset of grade III, for instance, may be a sign of placental insufficiency.
• Magnetic resonance imaging (MRI): This imaging approach relies on strong magnetic and radio waves to create highly detailed depictions of the fetus and placenta. Though not necessarily the first line of treatment, MRI may be used to diagnose placenta increta and percreta. In addition, this method may be used in cases of placental insufficiency.     

National Institutes of Health. Human Placenta Project: How does the placenta form? .

Rathbun K, Hildebrand J. Placenta abnormalities . StatPearls.

Hapugoda S, Jha P. Placenta: radiology reference article . Radiopaedia.

Hill M. Placenta development: embryology . University of New South Wales.

Gude N, Roberts C, Kalionis B, King R. Growth and function of the normal human placenta .

Krishna U, Bhalerao S. Placental insufficiency and fetal growth restriction .  J Obstet Gynaecol India . 2011;61(5):505-511.

By Mark Gurarie Gurarie is a freelance writer and editor. He is a writing composition adjunct lecturer at George Washington University.  

Jun 12, 2012

870 likes | 4.9k Views

PLACENTA. This is a fetomaternal organ. It has two components: Fetal part – develops from the chorionic sac ( chorion frondosum ) Maternal part – derived from the endometrium ( functional layer – decidua basalis )

Share Presentation

• severe bleeding
• secondary villi differentiate
• term placenta
• tertiary chorionic villi
• primary villi
• hormone production

Presentation Transcript

PLACENTA • This is a fetomaternal organ. • It has two components: • Fetal part – develops from the chorionic sac ( chorion frondosum ) • Maternal part – derived from the endometrium ( functional layer – decidua basalis ) • The placenta and the umbilical cord are a transport system for substances between the mother and the fetus.( vessels in umbilical cord ) • Function Of The Placenta: • Protection • Nutrition • Respiration • Excretion • Hormone production

Further Development of Chorionic Villi Early in the 3rd week, mesenchyme growth into the primary villi forming a core of mesenchymal tissue. Thus the Secondary Chorionic Villi are formed over the entire surface of the chorionic sac. Some mesenchymal cells in the secondary villi differentiate into capillaries and blood cells forming the Tertiary Chorionic Villi. The capillaries in the villi fuse to form arteriocapillary networks.

The previous formed arteriocapillary networks become connected with the embryonic heart through vessels which are formed in the mesenchyme of the chorion and connecting stalk. By the end of the 3rd week, embryonic blood begins to flow through the capillaries in the chorionic villi. Oxygen & nutrients in the maternal blood in the intervillous space diffuse through the walls of the villi and enter the embryo’s blood. Carbon dioxide & waste products diffuse from blood in the fetal capillaries through the wall of the chorionic villi into the maternal blood.

DECIDUA • This is the endometrium of the gravid (pregnant) uterus. • It has four parts: • Decidua basalis: it forms the maternal part of the placenta • Decidua capsularis: it covers the conceptus • Decidua parietalis: the rest of the endometrium • Decidua reflexa: • Junction between capsularis & parietalis.

DEVELOPMENT OF PLACENTA • Until the beginning of the 8th week, the entire chorionic sac is covered with villi. • After that, as the sac grows, only the part that is associated with Decidua basalis retain its villi. • Villi of Decidua capsularis compressed by the developing sac. • Thus, two types of chorion are formed: • Chorion frondosum (villous chorion) • Chorion laeve – bare (smooth) chorion • About 18 weeks old, it covers 15-30% of the decidua and weights about 1\ 6 of fetus

DEVELOPMENT OF PLACENTA • The villous chorion ( increase in number, enlarge and branch ) will form the fetal part of the placenta. • The decidua basalis will form the maternal part of the placenta. • The placenta will grow rapidly. • By the end of the 4th month, the decidua basalis is almost entirely replaced by the fetal part of the placenta.

FULL-TERM PLACENTA • Cotyledons –about 15 to 20 slightly bulging villous areas. Their surface is covered by shreds of decidua basalis from the uterine wall. • After birth, the placenta is always inspeced for missing cotyledons. Cotyledons remaining attached to the uterine wall after birth may cause severe bleeding. • Grooves – formerly occupied by placental septa • The fetal part of placenta; fetal membranes called developmental adnexa • Placenta;fetal membranes which are expelled are called afterbirth or secundina Maternal side

FULL-TERM PLACENTA( Discoid shape -500- 600 gm- Diameter 15-20 cm – Thicknessof 2-3 cm) • Fetal surface: • This side is smooth and shiny. It is covered by amnion. • The umbilical cord is attached close to the center of the placenta. • The umbilical vessels radiate from the umbilical cord. • They branch on the fetal surface to form chorionic vessels. • They enter the chorionic villi to form arteriocapillary-venous system. Fetal side

PLACENTAL CIRCULATION 80 to 100 each cotyledon - inflow

STRUCTURE OF STEM CHORIONIC VILLUS

PLACENTAL MEMBRANE knot –syncytiotrophoblast –Toward end of pregnancy – phagocytic cells • This is a composite structure that consists of the extrafetal tissues separating the fetal blood from the maternal blood. • It has four layers: • Syncytiotrophoblast • Cytotrophoblast • Connective tissue of villus • Endothelium of fetal capillaries • After the 20th week, the cytotrophoblastic cells disappear and the placental membrane consists only of three layers.

TRANSFER ACROSS THE PLACENTAL MEMBRANE Viruses: measles;poliomyelitis Microorganism: treponema pallidum of syphilis ; T.g which produce destructive change in the eye; brain . IgG( gamma globulin) , IgS;IgM ( immunoglobulin S;M )

Placental endocrine synthesis • The syncytiotrophoblast synthesizes protein &steroid hormones • The protein homones • 1- human chorionic gonadotropin • 2- h.c. somatomammotropin • 3-h.c. thyrotropin • 4-h.c. corticotropin • The steroid hormones • Progesterone & Estrogens

Third trimester bleeding is the common sign of these anomalies

Biscoid placentaBipartita Horseshoe

When villi persist on the entire surface of the chorionic sac ,a thin layer of placenta attaches to a large area of the uterus …… it is a membranous placenta.

FULL-TERM UMBILICAL CORD • Usually it is attached near the center of the fetal surface of placenta. • Length: about 50 cm • Diameter: 1-2 cm • Contains two arteries and one vein, surrounded by mucoid connective tissue (Wharton jelly) • The vessels are longer than the cord and may have loops (false knots).

• More by User

Placenta Previa

Placenta Previa. R.L. 33 y/o G4P3 (3002), PU 37 3/7 weeks AOG Married Filipino Roman Catholic. General Data. scheduled Cesarean section. Reason for consult. (-) hypertension (-) diabetes mellitus (-) bronchial asthma (-) thyroid disease No known allergies

2.59k views • 40 slides

Placenta accreta

Placenta accreta. Definition.

1.43k views • 20 slides

Placenta Previa. Hai Ho, MD Department of Family Practice. What is placenta previa?. Implantation of placenta over cervical os. Types of placenta previa. Who are at risk for placenta previa?. Endometrial scarring of upper segment of uterus – implantation in lower uterine segment

1.85k views • 44 slides

Project Placenta

Project Placenta. Ethan Jewett & Megan Lewis. Outline . Motivation Biological Background Goal Factors First model (arterial dilation) Expanded model (trophoblast invasion) Corrected arterial model Conclusion. Motivation.

578 views • 34 slides

Placenta. By Joshua Bower Peer Support 2013/2014 [email protected]. Learning Outcomes. Placenta Understand how the placenta forms and grows Know how the structure of the placenta is linked to its functions Know in principle the main functions of the placenta

976 views • 30 slides

The Placenta

Carissa Santos Nilani Singler. The Placenta. Description of the Placenta.

402 views • 8 slides

C. 4. B. NBL-S. 3. 3. 2. fluorescence ratio (log 2 ). SH-SY5Y. 1. 2. 0. 1. fluorescence ratio (log 2 ). -1. 0. (bp). -2. -1. 14900000. 15900000. 16900000. 17900000. -2. 0. 2E7. 4E7. 6E7. 8E7. 1E8. 120000000. (bp). 3. TNB-1. 2. fluorescence ratio (log 2 ).

214 views • 1 slides

PLACENTA. Placenta (plah-sen’tah) is a Latin word. It means “a flat cake”. Placenta is an organ characteristic of mammals, developing during pregnancy, joining mother and offspring, providing necessary provisions for the sustenance of developing human in intrauterine life.

1.61k views • 103 slides

Placenta. A Circular vascular structure that collects wastes. Placenta Previa. When the placenta is underneath the baby coming out first. Abruptio Placentae. When the placenta separates from the uterus prematurely. Amniotic Sac.

1.42k views • 30 slides

Placenta Previa. Ob & Gy Department, First Hospital, Xi ’ an Jiao Tong University SHU WANG. Definition. This is where a placenta is inserted partially or wholly in the lower uterine segment. pictures. placenta Previa. placenta Previa. Etiology. Endometrium disorder and injury

1.84k views • 16 slides

Placenta delivered

Placenta delivered.

413 views • 36 slides

Everything you need to know about Placenta Position & Placenta Health – with FAQs

Medically Reviewed by: Dr. Veena Shinde (M.D, D.G.O,  PG – Assisted Reproductive Technology (ART) from Warick, UK) Mumbai, India

• >> Post Created: November 15, 2021
• >> Last Updated: September 10, 2024

When a woman gets pregnant, there are new things for her to learn every day; about the pregnancy –  morning sickness ,  pre-natal screening …; the would-be baby, her ever-changing body, and everything that her body is doing for the unborn baby.

By now, your doctor might mention the words ‘Placenta’ and ‘Placenta Position’ a number of times. The Placenta is one of the most vital organ during pregnancy, and it is imperative that you understand everything about it, like position of your placenta – like fundal placenta (placenta on top), anterior placenta (Placenta in front), posterior placenta (placenta towards the back) and so on… and placenta health –  placenta related complications and so on.

With this article, we aim to answer all your questions regarding placenta and how each placenta position influences your pregnancy journey and the delivery of your baby. That’s not all look at what all you can do to maintain placental health and what you need to avoid to stay away from complications. 

Placenta Position - Table of Contents

What is placenta.

A woman’s body is truly a biological wonder! When she conceives, her body changes in a number of ways to nourish and protect her growing baby in the womb.

One such important change that her body makes is the development of an organ called the ‘Placenta’ when she is 3 weeks into her pregnancy. It is developed from the fertilized ovum or egg. The organ can be detected through an ultrasound test at 12 weeks. The baby is connected to the Placenta through an umbilical cord for the supply of oxygen and nutrients required for it to grow. It also gets rid of the waste from the blood of your baby.

The placenta is one of the most vital organs during pregnancy, because apart from keeping the baby nourished and safe it also produces hormones that are essential during pregnancy. Estrogen, Progesterone and Lactogen – these hormones have an extremely responsible task of keeping the mother’s and baby’s blood separate to prevent infections. 

Why does the placenta position matter?

After understanding the vital role of this organ in pregnancy, what position your placenta is in? – is another important subject that you need to understand.

Normally, the position of your placenta does not have any effect on the pregnancy or the baby, except if it is in a position where it blocks the cervix (opening of the womb); this position is called the Placenta Previa. If the placenta position in a pregnant woman is Placenta Previa then she has to be closely monitored and is likely to give birth through caesarean-section.

You can say that the placenta position can become a determining factor to know whether a vaginal or a C-section delivery is safer.

Further bear in mind the position of your placenta is something that happens naturally and it cannot be planned by you or your doctor. There are various stages for placenta development as well.

Placenta Position Diagnosis

How do you come to know what placenta position you have.

An ultrasound done around the level 2 of your mid-pregnancy ultrasound or anatomy scan, provides your doctor a clear indication of your placental placement. These scans happen generally around 20 weeks of your pregnancy. However earlier scans too can provide an indication of the placement of your placenta. 

Different types of placenta positions

The egg implants itself within the uterus upon fertilization, and that’s where the placenta is positioned.

So, your placenta could be on the top of the uterus (fundal placenta) or on the back wall of the uterus (posterior placenta) or front wall within the uterus (anterior placenta) or even low lying placenta – towards the bottom (near the cervix or even over) etc…

However, the position of your placenta could change over time as the uterus expands and your baby grows. Your initial, screening/ultrasound scans between the 12 th  week and the 20 th  week can help determine the placenta position and its movements.

Here are the various placental positions which your placenta implants itself within the uterus:

Fundal Placenta

Anterior placenta, posterior placenta.

• Lateral Placenta Positions
• Placenta Previa (Low-lying placenta)

It is most common placenta implantation position, wherein the placenta is positioned on the top of the uterus. Complications in pregnancies with this position are negligible and is considered to be an ideal position for delivery.

However,  research  has found an increased connection between the fundal placenta and preterm premature rupture of membranes (PPROM), which means that there are higher chances of the water breaking before 37 weeks of pregnancy. The possibility of this happening is however just  3% of total pregnancies  – which means PPROM happening while having a fundal placenta would be even a further minuscule percentage.

Basically the risk is that when the placenta is at the top of the uterus (fundal placenta), the placenta builds the weakest point of the membrane over the opening of the womb, which in turn could lead to  premature rupture of membranes .

When the placenta is located in front of the uterus, the position is called Anterior Placenta .

With Anterior Placenta come a few things which would feel different than other pregnant women, like delayed flutters or delayed fetal movements, difficulty in heart beat detection earlier on and so on.

Its not because there is anything wrong with you or your baby. Its just the placement of your placenta is right in the front of your uterus which acts as a cushion causing you to feel slow or mild baby movements in the initial phase of your pregnancy. The same is true when it comes to detecting your child’s heartbeat as well.

In case of  posterior placenta , the placenta is positioned towards the back of the uterus. In this position, the baby’s movements can be felt a little more effectively and earlier in pregnancy. This placenta position also helps the baby be in the best position for birth.

However, as the uterus’ back wall is thicker and longer, the blood flow might not have the best efficiency, which might raise the  risk  of a preterm labor.

Lateral Placenta

When the placenta is positioned in the right or the left side of the uterus, it is known as lateral placenta positions. These 2 positions are also referred to as Right Lateral Position & Left Lateral Position respectively.

These positions are usually not common. In such cases, the baby gets constant blood flow from one of the uterine and/or ovarian arteries, along with some more from the other uterine artery.

This in turn can increase the risk of pre-eclampsia , caused by high blood pressure. Some research has also associated lateral placenta to higher chances of having a ‘breech baby’ – a baby who’s lying feet-first at the opening of the uterus, instead of the ideal head-first position.

Placenta Previa

Placenta Previa is one of the position that can truly be a cause of concern. It is rare, seen in roughly 1 out of 200 pregnancies. In this case, the placenta covers the cervix partially or completely. If the placenta covers the cervix completely, then a caesarean section is the only safe way to deliver the baby.

What can cause placenta previa?

Factors that can cause or increase the chances of placenta previa :

• If the age of the mother is over 35 years
• If the mother is pregnant with twins or multiples
• If you had Placenta Previa in a previous pregnancy
• If you had C-section in a previous pregnancy
• If you were smoking during pregnancy

Placenta previa can be checked through regular ultrasound scans or if there is maternal vaginal bleeding. If diagnosed with placenta previa, then an additional ultrasound scan will be required at 32-week gestation period to understand the severity of the condition and the possible ways to manage it in the third trimester.

The biggest risk with the placenta covering the cervix is major bleeding and that too without any warning. If diagnosed with the condition, the expectant mother will need to be on complete bed rest starting from 34 weeks, with or without any bleeding.

Note: Contact your hospital at the slightest bleeding. If there’s significant bleeding, then the baby might have to be delivered pre-maturely.

Continue reading below ↓

Read this next

When does morning sickness end? And common related FAQ’s

Sequential Screening – Why is it so important for you to get it done?

hCG levels twins vs. singleton – What’s the difference?

Placenta position & placenta health - common faqs, q. can the placenta position change in pregnancy.

The position of your placenta could change as the uterus stretches to make space for your growing baby. This is common and nothing to worry about as such.

So, whether you have a placenta posterior , anterior placenta or even low-lying placenta , the position of your placenta could change by the time of your delivery due to uterus expansion and your growing baby.

Q. How do you determine the placenta position?

The developed placental position is visible through an ultrasound by the 12 th  week of pregnancy. The position of the placenta at the cervix (whether it is covering the cervix partially or completely) can be determined at the 20 th  week ultrasound scan (also called Morphology Scan).

Q. How much does the placenta position matter?

If you have a posterior placenta , anterior placenta or even fundal placenta placement, then there isn’t generally a cause for concern. Nonetheless, in case you have placenta previa then there is something to be worried about as the placenta covers the cervix.

There is no medical cure for placenta previa , but treatments are present to ease the difficulties it may cause during pregnancy. Treatment can vary based on the placenta previa position, whether it is complete or partial (blocks cervix completely or partially), amount of bleeding, fetal position and gestational age. The most important diagnosis is complete best rest for the expectant mother and regular, close monitoring of the baby and the mother.

Q. What are the common placenta problems?

Placenta problems in pregnancy can cause heavy vaginal bleeding. Possible placenta problems can be placenta previa, placenta abruption, placenta accrete, and retained placenta.

• Placenta previa  is a condition wherein the placenta completely or partially covers the cervix or the mouth of the womb. This placenta position is commonly seen in early pregnancy stages, but is usually fixed in the later stages, as the uterus grows. However, if the placenta previa prevails even in the third trimester, then C-section is the only way to deliver the baby.

It is important to note that this condition can result in heavy vaginal bleeding during pregnancy or even during birth. Effective management of the condition will depend upon –

• Amount of bleeding
• Whether or not and how swoon the bleeding stops
• The number of weeks into pregnancy
• Placenta position
• Baby’s health
• Placenta abruption  is a condition when the placenta ‘peels away from the inner walls of the uterus’ before delivery. This will not only result in insufficient supply of oxygen and nutrients to the baby, but also heavy bleeding for the mother. This can give rise to an emergency condition, and hence, will need an early delivery.
• Placenta accrete  is the condition when the placenta, which should separate itself from the uterine wall after delivery of the baby, continues to stay firmly attached to the uterus. This condition too can cause major blood loss during delivery. In extreme case, if the placenta grows through the uterine wall or overruns the muscles of the uterus, then the doctor will not only recommend a C-section delivery, but also the removal of the uterus after the baby is delivered.
• Retained placenta  is a condition when the placenta is not delivered within 30 minutes of the baby’s delivery. This can happen due to two reasons – if the placenta is still stuck to the uterine wall or if it is unable to come out because of a partially closed cervix. This needs to be rectified urgently, as it can cause major blood loss or severe infection.

Q. How is the placenta delivered?

In what is called as the third stage of labor, the placenta is delivered after the baby. If the baby is vaginally delivered, then so is the placenta. Even after birth, the mother will continue to have mild contractions, for which the doctor might prescribe oxytocin (Pitocin) to continue uterine contractions and reduce postpartum bleeding.

The doctor might also massage the lower abdomen to urge the uterus to contract and get the placenta out. The mother may be asked to push once more to deliver the placenta if the childbirth has happened through the vagina.

In case of a C-section delivery, the doctor will remove the placenta during the procedure itself.

Once out of the body, the doctor will inspect the placenta to ensure that it’s intact and that none of its fragments remain in the body, as it can cause bleeding and infection.

Q. What affects placenta health?

Placenta health can be affected by a number of factors.

• Mother’s age: If the mother’s age is over 40 years, then some problems with placenta are common.
• High Blood Pressure
• Twin or multiple pregnancy: With more than one baby in the womb, some placental problems become common.
• Water breaking before labor: In the womb, the baby is kept safe in every way by a membrane (called amniotic sac) filled with fluid. If the sac leaks or breaks before labor, then it can cause some placental issues.
• Blood-clotting disorder
• Previous surgery on the uterus: If the previous pregnancy was through a C-section or any other surgery like the removal of fibroids has been performed on the uterus, then brace yourself for some possible placental complications.
• Previous placental problems
• Smoking or addiction to cocaine or other substances during pregnancy can cause placenta issues.
• Abdominal trauma: A shock or trauma to the pregnant abdomen by a fall or a blow can increase the chances of placenta abruption, wherein the placenta is separated from the uterus.

Q. How to reduce risk of placental problems?

Placenta issues cannot be avoided completely. However, there are certain ways to ensure a healthy pregnancy:

• Go for regular check-ups and ultrasound scans to determine the position and health of the baby and the placenta.
• Consult your doctor immediately to handle any other health condition like high blood pressure, diabetes, etc.
• Do not smoke or consume drugs.
• Eat healthy and stay active with regular walks or exercises as advised by your doctor
• Discuss the possible risks with the doctor to go ahead with an elective C-section.
• Inform the doctor about the following beforehand
• Placental problem in the previous surgery
• Any past surgery on the uterus

This way, the doctor will be able to guide the expectant mother better, reduce the possibility of suffering through the condition again, and monitor the condition of the mother more closely.

Q. What are the signs of a placenta problem during pregnancy? When to call the doctor?

Placental problems usually come without a warning and are mostly severe. Therefore, if a pregnant woman experiences the following, she should be rushed to the doctor –

• Vaginal Bleeding, irrespective of the amount
• Constant or fast contractions
• Reduced fetal movement
• Severe back pain
• Hard tummy that isn’t relaxing

Key Takeaway

The placenta and placenta position have an extremely vital role to play in the nurturing of the baby in the womb. Therefore, every mother should learn about it and never hesitate to discuss with your doctor about the slightest concern or query you have about your placenta health and placenta position.

After all the growth of your baby is related to not only your health but your placentas health as well.

Further remember placenta position happens naturally in your body wherever the egg implants itself after fertilization. You don’t have a control over. But understand what each position will definitely help you sail through your pregnancy.  

So, understand the importance of placenta – after all, the placenta is the organ that joins the mother and the baby!

Happy Pregnancy!

Palak Thakkar

You may also be interested in.

Pregnant with Twins or multiples – Frequently asked Questions

Postpartum Preeclampsia—A Complete Guide

Posterior Placenta: Busting Myths & Understanding Facts + FAQs

First Trimester Screening: What You Need to Know?

Anterior Placenta Position – How It Affects Pregnancy, Labor and Delivery

3 thoughts on “everything you need to know about placenta position & placenta health – with faqs”.

I was looking for information on placenta position for my wife as doc said she has placenta previa. Superb article. Nicely written for a layman to understand. Very helpful.

Thanks David for visiting and appreciating the article. I am glad you found answers to your queries.

Usually I don’t read post on blogs, but I wish to say that this write-up very forced me to try and do so!

Comments are closed.

Subscribe to get our latest posts on parenting and we will make sure you don’t miss a thing!

Privacy Policy - Terms and Conditions

Warning: The NCBI web site requires JavaScript to function. more...

An official website of the United States government

The .gov means it's official. Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you're on a federal government site.

The site is secure. The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

• Publications
• Account settings
• Browse Titles

NCBI Bookshelf. A service of the National Library of Medicine, National Institutes of Health.

StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 Jan-.

StatPearls [Internet].

Placenta abnormalities.

Kimberly M. Rathbun ; Jason P. Hildebrand .

Affiliations

Last Update: October 17, 2022 .

• Continuing Education Activity

The placenta attaches to the uterine wall and allows metabolic exchange between the fetus and the mother; it has both embryonic and maternal components. The embryonic portion comes from the outermost embryonic membrane, whereas the maternal portion develops from the decidua basalis of the uterus. The placental membrane separates the embryonic blood from maternal blood but is thin enough to allow diffusion and transport of nutrients and waste. A normal placenta is round or oval-shaped and about 22 cm in diameter. It is 2 cm to 2.5 cm thick and weighs about a pound. This activity reviews placental abnormalities and the role of the interprofessional team in the evaluation of this condition.

• Determine the risk of placenta accreta.
• Identify common placental variants.
• Assess the clinical significance of an abnormal placenta.
• Identify some interprofessional team strategies for evaluating patients with placental abnormalities to produce the best outcomes.
• Introduction

The placenta attaches to the uterine wall and allows metabolic exchange between the fetus and the mother. The placenta has both embryonic and maternal components. The embryonic portion comes from the outermost embryonic membrane. The maternal portion develops from the decidua basalis of the uterus. The placental membrane separates the embryonic blood from maternal blood but is thin enough to allow diffusion and transport of nutrients and waste. A normal placenta is round or oval-shaped and about 22 cm in diameter. It is 2 cm to 2.5 cm thick and weighs about a pound.

• Issues of Concern

Placenta Accreta

Placenta accreta is the abnormal adherence of the placenta to the myometrium, associated with partial or complete absence of the decidua basalis and an abnormally or incompletely developed fibrinoid Nitabuch layer. [1] When normally developed, these layers represent the cleavage line, allowing a normal third stage of labor. The prevalence of this condition has been increasing and now occurs in 1 of 2500 pregnancies. [2] The incidence of placenta accreta increases in women with previous cesarean delivery, other uterine surgery, advanced maternal age, high gravidity, multiparity, previous curettage, and placenta previa. [1] [3] [1]  The highest risk for a placenta accreta is in pregnancies with a history of a cesarean section and a current placenta previa. [3] [1] [2] [4]

Risk of placenta accreta  

The risk of placenta accreta with a concomitant placenta previa (posterior or anterior) increases with each uterine surgery

• No previous uterine surgery: 1% to 5%    
• One previous Cesarean section: 3%    
• Two previous Cesarean sections: 11%     
• Three previous Cesarean sections: 40%    
• Four previous Cesarean sections: 61%     
• Five or more previous Cesarean sections: 67%   [1] [2] [3] [2] [4]

Ultrasound features suggestive of placenta accreta include deficiency of retroplacental sonolucent zone, vascular lacunae, myometrial thinning, and interruption of the bladder line. [2] Grayscale sonography has a sensitivity of 77% to 87% and a specificity of 96% to 98% for placenta accreta. [1] [2]  MRI does not appreciably improve diagnostic accuracy when compared to ultrasonography. An attempt to deliver an adherent placenta can result in hemorrhage, shock, and uterine inversion. [1] Hysterectomy traditionally treated placenta accreta, but uterus-conserving treatments are now commonly used. [1]

Placenta Increta

Placenta increta is a form of placenta accreta in which the placental villi penetrate the uterine muscle (myometrium) but do not penetrate the uterine serosa. [1] Placenta increta accounts for approximately 15% to 17% of all placenta accreta cases.

Placenta Percreta

Placenta percreta is a form of placenta accreta in which the placental villi penetrate the myometrium to the uterine serosa. [1] Placenta percreta accounts for approximately 5% to 7% of all placenta accreta cases.

Placenta Previa 

Placenta previa occurs when the placenta implants totally or partially in the lower segment of the uterus rather than in the fundus. In complete previa, the internal os is completely covered by the placenta. [1] In partial previa, the placenta covers a portion of the internal os. [1] [5] In marginal previa, the edge of the placenta extends to the edge of the cervical os. [1] [5] [1]  A low-lying placenta is commonly defined as one within 2 cm of the cervical os without covering any portion. [1] These conditions occur in approximately 1 in 200 to 250 pregnancies, and risk factors include prior cesarean delivery, previous abortion, prior intrauterine surgery, smoking, multifetal gestation, increasing parity, and maternal age. [1] [5] [1]  A woman with a history of placenta previa is 12 times more likely to have placenta previa in a subsequent pregnancy. Ultrasound screening programs during first and early second-trimester pregnancies now include placental localization. [1] Transvaginal ultrasound can also make a diagnosis. Delivery should be by Cesarean section as dilation of the cervix causes separation of the placenta, leading to bleeding from the open vessels. [1] [5]  Vaginal delivery is an option for those with low-lying placentas as the bleeding morbidity has proven to be limited. [1] [5]

Placental Variants

Bilobed placenta

A bilobed placenta (placenta bilobate, bipartite placenta, placenta duplex) is a placenta with 2 roughly equal-sized lobes separated by a membrane. It occurs in 2% to 8% of placentas. The umbilical cord may be inserted in either lobe, velamentous, or between the lobes. While there is no increased risk of fetal anomalies with this abnormality, bilobed placentas can be associated with first-trimester bleeding, polyhydramnios, abruption, and retained placenta. A placenta with more than 2 lobes is rare, as is a multilobate placenta. 

Succenturiate placenta 

The succenturiate placenta is a condition in which 1 or more accessory lobes develop in the membranes apart from the main placental body, to which vessels of fetal origin usually connect them. It is a smaller variant of a bilobed placenta. The vessels are supported only by communicating membranes. If the communicating membranes do not have vessels, it is called placenta supuria. This condition occurs in 5% of placentas. Advanced maternal age and in vitro fertilization are risk factors for the succenturiate placenta. Other factors leading to succenturiate placentas include implantation over leiomyomas, in areas of previous surgery, in the cornu, or over the cervical os. Ultrasound, particularly color Doppler, can be used to identify this condition. The risks of vasa previa and retained placenta increase with this condition, like bilobed and multilobate placentas.

Circumvallate placenta

Circumvallate placenta is an extrachorial, annularly-shaped placenta with raised edges composed of a double fold of chorion, amnion, degenerated decidua, and fibrin deposits. [6] In this condition, the chorionic plate is smaller than the basal plate, resulting in hematoma retention in the placental margin. [6] Within the ring, the fetal surface has the usual appearance except that the large vessels terminate abruptly at the margin of the ring. The circumvallate placenta is associated with poor pregnancy outcomes due to an increased risk of vaginal bleeding beginning in the first trimester, premature rupture of the membranes (PROM), preterm delivery, placental insufficiency, and placental abruption. [6] The diagnosis is difficult to make during pregnancy and is often made on visual inspection of the placenta after delivery.

A circummarginate placenta is an extrachorial placenta similar to a circumvallate placenta, except that the transition from membranous to villous chorion is flat. This form is clinically insignificant.

Placenta membranacea 

Placenta membranacea is a rare placental abnormality where chorionic villi cover fetal membranes either completely (diffuse placenta membranacea) or partially (partial placenta membranacea), and the placenta develops as a thin structure occupying the entire periphery of the chorion. [7] Clinically the abnormality can present with vaginal bleeding in the second or third trimester, which is often painless or during labor. [7] Other placenta abnormalities, such as placenta previa and placenta accreta, can be associated with this condition. [7]   Ultrasound has been reported as a diagnostic tool for this condition, but there is no data on its sensitivity and specificity due to its rarity. [7]

Ring-shaped placenta

The ring-shaped placenta is annularly-shaped, a variant of placenta membranacea. It can sometimes be a complete ring of placental tissue, but more often, tissue atrophy in a portion of the ring results in a horseshoe shape. The incidence is less than 1 in 6000. The ring-shaped placenta can cause antepartum, postpartum bleeding, and fetal growth restriction.

Placenta fenestrata

Placenta fenestrata is a rare condition in which the central portion of the discoid placenta is missing. Rarely, there may be an actual hole in the placenta, but more frequently, the defect involves the villous tissue, and the chorionic plate remains intact. At delivery, this finding may cause concern for retained placenta.

Battledore placenta

Battledore placenta (marginal cord insertion) is where the umbilical cord is inserted at or near the placental margin rather than in the center. The cord can be inserted as close to 2 cm from the edge of the placenta (velamentous cord insertion). The incidence is 7% to 9% of singleton pregnancies and 24% to 33% of twin pregnancies. Complications associated with battledore placenta are preterm labor, fetal distress, and intrauterine growth restriction.

• Clinical Significance

The placenta is a maternal-fetal organ that begins developing at blastocyst implantation and is delivered at birth with the fetus. The fetus relies on the placenta for nutrition and many developmentally essential functions. Abnormalities range from those anatomically associated with the degree or site of implantation, those of structure and placental function, to placenta-maternal effects such as pre-eclampsia and fetal erythroblastosis, and finally, mechanical abnormalities associated with the umbilical cord. The evaluation of the placenta and cord plays an important role in determining the viability of the fetus and, ultimately, the infant delivered.

• Enhancing Healthcare Team Outcomes

While the obstetrician manages routine pregnancy, complex cases that involve placental abnormalities are usually managed by an interprofessional team that includes the intensivist, hematologists, labor and delivery nurses, and anesthesiologists. Most placental abnormalities come to light just before or during delivery. With the advent of ultrasound, most serious placental abnormalities are identified before delivery. One of the most serious morbidities with placental abnormalities is the potential for hemorrhage; hence, a team approach is necessary to ensure the mother's and the infant's safety.

• Review Questions
• Access free multiple choice questions on this topic.
• Comment on this article.

Disclosure: Kimberly Rathbun declares no relevant financial relationships with ineligible companies.

Disclosure: Jason Hildebrand declares no relevant financial relationships with ineligible companies.

This book is distributed under the terms of the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0) ( http://creativecommons.org/licenses/by-nc-nd/4.0/ ), which permits others to distribute the work, provided that the article is not altered or used commercially. You are not required to obtain permission to distribute this article, provided that you credit the author and journal.

• Cite this Page Rathbun KM, Hildebrand JP. Placenta Abnormalities. [Updated 2022 Oct 17]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 Jan-.

In this Page

Bulk download.

• Bulk download StatPearls data from FTP

Related information

• PMC PubMed Central citations
• PubMed Links to PubMed

Similar articles in PubMed

• Metabolism of glucose by fetus and placenta of sheep. The effects of normal fluctuations in uterine blood flow. [J Dev Physiol. 1987] Metabolism of glucose by fetus and placenta of sheep. The effects of normal fluctuations in uterine blood flow. Gu W, Jones CT, Harding JE. J Dev Physiol. 1987 Aug; 9(4):369-89.
• Interactions between trophoblast cells and the maternal and fetal circulation in the mouse placenta. [Dev Biol. 2002] Interactions between trophoblast cells and the maternal and fetal circulation in the mouse placenta. Adamson SL, Lu Y, Whiteley KJ, Holmyard D, Hemberger M, Pfarrer C, Cross JC. Dev Biol. 2002 Oct 15; 250(2):358-73.
• Review Endocrine regulation of human fetal growth: the role of the mother, placenta, and fetus. [Endocr Rev. 2006] Review Endocrine regulation of human fetal growth: the role of the mother, placenta, and fetus. Murphy VE, Smith R, Giles WB, Clifton VL. Endocr Rev. 2006 Apr; 27(2):141-69. Epub 2006 Jan 24.
• Review An integrated model of preeclampsia: a multifaceted syndrome of the maternal cardiovascular-placental-fetal array. [Am J Obstet Gynecol. 2022] Review An integrated model of preeclampsia: a multifaceted syndrome of the maternal cardiovascular-placental-fetal array. Yagel S, Cohen SM, Goldman-Wohl D. Am J Obstet Gynecol. 2022 Feb; 226(2S):S963-S972. Epub 2021 Mar 9.
• Review The placenta. Not just a conduit for maternal fuels. [Diabetes. 1991] Review The placenta. Not just a conduit for maternal fuels. Hay WW Jr. Diabetes. 1991 Dec; 40 Suppl 2:44-50.

Recent Activity

• Placenta Abnormalities - StatPearls Placenta Abnormalities - StatPearls

Your browsing activity is empty.

Activity recording is turned off.

Turn recording back on

Connect with NLM

National Library of Medicine 8600 Rockville Pike Bethesda, MD 20894

Web Policies FOIA HHS Vulnerability Disclosure

Help Accessibility Careers

• Mammary Glands
• Fallopian Tubes
• Supporting Ligaments
• Reproductive System
• Gametogenesis
• Placental Development
• Maternal Adaptations
• Menstrual Cycle
• Antenatal Care
• Small for Gestational Age
• Large for Gestational Age
• RBC Isoimmunisation
• Prematurity
• Prolonged Pregnancy
• Multiple Pregnancy
• Miscarriage
• Recurrent Miscarriage
• Ectopic Pregnancy
• Hyperemesis Gravidarum
• Gestational Trophoblastic Disease
• Breech Presentation
• Abnormal lie, Malpresentation and Malposition
• Oligohydramnios
• Polyhydramnios

Placenta Praevia

• Placental Abruption
• Pre-Eclampsia
• Gestational Diabetes
• Headaches in Pregnancy
• Haematological
• Obstetric Cholestasis
• Thyroid Disease in Pregnancy
• Epilepsy in Pregnancy
• Induction of Labour
• Operative Vaginal Delivery
• Prelabour Rupture of Membranes
• Caesarean Section
• Shoulder Dystocia
• Cord Prolapse
• Uterine Rupture
• Amniotic Fluid Embolism
• Primary PPH
• Secondary PPH
• Psychiatric Disease
• Postpartum Contraception
• Breastfeeding Problems
• Primary Dysmenorrhoea
• Amenorrhoea and Oligomenorrhoea
• Heavy Menstrual Bleeding
• Endometriosis
• Endometrial Cancer
• Adenomyosis
• Cervical Polyps
• Cervical Ectropion
• Cervical Intraepithelial Neoplasia + Cervical Screening
• Cervical Cancer
• Polycystic Ovary Syndrome (PCOS)
• Ovarian Cysts & Tumours
• Urinary Incontinence
• Genitourinary Prolapses
• Bartholin's Cyst
• Lichen Sclerosus
• Vulval Carcinoma
• Introduction to Infertility
• Female Factor Infertility
• Male Factor Infertility
• Female Genital Mutilation
• Barrier Contraception
• Combined Hormonal
• Progesterone Only Hormonal
• Intrauterine System & Device
• Emergency Contraception
• Pelvic Inflammatory Disease
• Genital Warts
• Genital Herpes
• Trichomonas Vaginalis
• Bacterial Vaginosis
• Vulvovaginal Candidiasis
• Obstetric History
• Gynaecological History
• Sexual History
• Obstetric Examination
• Speculum Examination
• Bimanual Examination
• Amniocentesis
• Chorionic Villus Sampling
• Hysterectomy
• Endometrial Ablation
• Tension-Free Vaginal Tape
• Contraceptive Implant
• Fitting an IUS or IUD

Original Author(s): Alice Reid Last updated: 8th March 2022 Revisions: 5

• 1 Pathophysiology
• 2 Risk Factors
• 3.1.1 History
• 3.1.2 General Examination
• 3.1.3 Assessment of Bleeding
• 4 Differential Diagnoses
• 5.1 Haematology
• 5.2 Biochemistry
• 5.3 Assess Fetal Wellbeing
• 5.4 Imaging
• 6 Management

Placenta praevia  is where the placenta is fully or partially attached to the lower uterine segment. It is an important cause of antepartum haemorrhage – vaginal bleeding from week 24 of gestation until delivery.

In this article, we shall look at the pathophysiology, clinical features and management of placenta praevia .

Pathophysiology

Placenta praevia  is where the placenta is fully or partially attached to the lower uterine segment. There are two main types:

• Minor placenta praevia  – placenta is low but does not cover the internal cervical os.
• Major placenta praevia  – placenta lies over the internal cervical os.

A low-lying placenta is more susceptible to  haemorrhage , possibly due to a defective attachment to the uterine wall. Bleeding can be spontaneous, or provoked by mild trauma (e.g vaginal examination). Additionally, the placenta may be damaged as the presenting part of the fetus moves into the lower uterine segment in preparation for labour.

Fig 1 – Placenta praevia is where the placenta is attached to the lower uterine segment.

Risk Factors

The main risk factor for placenta praevia is  previous caesarean section.  There is a 1 in 160 incidence associated with 1 previous section – this rises to 1 in 60 with 2 previous sections, to 1 in 10 with 4 sections.

The other risk factors include:

• High parity
• Maternal age >40 years
• Multiple pregnancy
• Previous placenta praevia
• History of uterine infection (endometritis)
• Curettage to the endometrium after miscarriage or termination

Clinical Features

Any woman presenting with  antepartum haemorrhage  (APH) should be assessed in a systematic manner (see box below).

Placenta praevia classically presents as  painless vaginal bleeding , this can vary between spotting to massive haemorrhage. There can be pain if the woman is in labour.

Examination may reveal risk factors pertinent to placenta praevia – e.g. c-section scar or multiple pregnancy. The uterus is usually not tender on palpation.

Assessment of Antepartum Haemorrhage

The following questions are useful to ask in the assessment of antepartum haemorrhage:

• How much bleeding was there and when did is start?
• Was it fresh red or old brown blood, or was it mixed with mucus?
• Could the waters have broken (membranes ruptured?)
• Was it provoked (post-coital) or not?
• Is there any abdominal pain?
• Are the fetal movements normal?
• Are there any risk factors for abruption? e.g. smoking/drug use/trauma – domestic violence is an important cause.

If the bleed is ongoing, or if there has been a significant vaginal bleed,  ABC assessment and resuscitation  is vital. If the woman is clinically stable, proceed to examination.

General Examination

On general examination, the following should be assessed:

• Pallor, distress, check capillary refill, are peripheries cool?
• Is the abdomen tender?
• Does the uterus feel ‘woody’ or ‘tense’ (which may indicate placental abruption)?
• Are there palpable contractions?
• Check the lie and presentation of the fetus/fetuses. Ultrasound can be used to help.
• Check fetal wellbeing with a cardiotocograph (CTG) at 26 weeks gestation or above: (otherwise auscultate the fetal heart only).
• Read the hand-held pregnancy notes: are there scan reports? This will be helpful in establishing whether there could be placenta praevia

Assessment of Bleeding

Lastly, the bleeding itself should be assessed:

• Externally  e.g. by looking at pads.
• Look for whether blood is fresh red or dark. How much blood is there? Are there clots? Are there any cervical lesions? Is there any cervical dilatation, or any chance that the membranes have ruptured?
• Take triple genital swabs  to exclude infection if the bleeding is minimal
• In minor bleed, when placenta praevia is excluded, it can help to establish whether the cervix is beginning to dilate.
• Avoid digital VE if the membranes have ruptured.

Differential Diagnoses

Placenta praevia is an important cause of  antenatal haemorrhage ; but it is not the most common. Differential diagnoses to consider include:

• Placental abruption   – where a part or all of the placenta separates from the wall of the uterus prematurely.
• The bleeding occurs following membrane rupture when there is rupture of the umbilical cord vessels, leading to loss of fetal blood and rapid deterioration in fetal condition.
• Uterine rupture   – a full-thickness disruption of the uterine muscle and overlying serosa. This usually occurs in labour with a history of previous caesarean section or previous uterine surgery such as myomectomy.
• Benign or malignant lesions – e.g. polyps , carcinoma. cervical ectropion (common).
• Infections – e.g. candida , bacterial vaginosis and chlamydia .

Fig 2 – Cervical ectropion on speculum examination. This is a common cause of antepartum haemorrhage.

Investigations

If major bleeding is suspected, resuscitate and perform investigations simultaneously.

Haematology

• Full blood count  – assess any maternal anaemia.
• Clotting profile
• Kleihauer test  – if the woman is Rhesus negative (to determine the amount of  feto-maternal haemorrhage  and thus the dose of Anti-D required).
• Group and Save  – if blood group is unknown.
• Cross-match  – if the clinical presentation is likely to warrant transfusion.

Biochemistry

These are performed to exclude hypertensive disorders including pre-eclampsia and HELLP syndrome, and any other organ dysfunction:

• Urea and electrolytes
• Liver function tests

Assess Fetal Wellbeing

In women above 26 weeks gestation, a cardiotocograph (CTG) should be performed to assess fetal wellbeing.

The definitive diagnosis of placenta praevia is via ultrasound . There is a short distance between the lower edge of the placenta and internal os.

Fig 3 – Anterior placenta previa. The placenta (arrow) has covered the internal os completely (arrowhead).

Any woman presenting with a significant antepartum haemorrhage should be resuscitated using an  A BCDE approach . Do not delay maternal resuscitation in order to determine fetal viability.

Placenta praevia may be identified in an asymptomatic patient at their  20-week ultrasound scan :

• Placenta praevia minor  – a repeat scan at 36 weeks is recommended, as the placenta is likely to have moved superiorly.
• Placenta praevia major  – a repeat scan at 32 weeks is recommended, and a plan for delivery should be made at this time.

In cases of confirmed placenta praevia,  Caesarean section  is the safest mode of delivery. Placenta praevia major usually warrants an elective Caesarean section at 38 weeks.

In all cases of antepartum haemorrhage, give anti-D within 72 hours of the onset of bleeding if the woman is rhesus D negative.

Placenta praevia  is where the placenta is fully or partially attached to the lower uterine segment. It is an important cause of antepartum haemorrhage - vaginal bleeding from week 24 of gestation until delivery.

• Minor placenta praevia  - placenta is low but does not cover the internal cervical os.
• Major placenta praevia  - placenta lies over the internal cervical os.

The main risk factor for placenta praevia is  previous caesarean section.  There is a 1 in 160 incidence associated with 1 previous section - this rises to 1 in 60 with 2 previous sections, to 1 in 10 with 4 sections.

[start-clinical]

[end-clinical]

• Placental abruption   - where a part or all of the placenta separates from the wall of the uterus prematurely.
• Uterine rupture   - a full-thickness disruption of the uterine muscle and overlying serosa. This usually occurs in labour with a history of previous caesarean section or previous uterine surgery such as myomectomy.
• Benign or malignant lesions - e.g. polyps , carcinoma. cervical ectropion (common).
• Kleihauer test  - if the woman is Rhesus negative (to determine the amount of  feto-maternal haemorrhage  and thus the dose of Anti-D required).
• Group and Save  - if blood group is unknown.
• Cross-match  - if the clinical presentation is likely to warrant transfusion.

Found an error? Is our article missing some key information? Make the changes yourself here!

Once you've finished editing, click 'Submit for Review', and your changes will be reviewed by our team before publishing on the site.

We use cookies to improve your experience on our site and to show you relevant advertising. To find out more, read our privacy policy .

Privacy Overview