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Placenta Accreta

By Julie S. Moldenhauer, MD, Associate Professor of Clinical Obstetrics and Gynecology in Surgery, The Garbose Family Special Delivery Unit, The Center for Fetal Diagnosis and Treatment, Children's Hospital of Philadelphia; Attending Physician, The University of Pennsylvania Perelman School of Medicine

Placenta accreta is a placenta with an abnormally firm attachment to the uterus.

  • Having had both a cesarean delivery and placenta previa in a previous pregnancy greatly increases the risk of placenta accreta.

  • If women have risk factors for placenta accreta, doctors do ultrasonography periodically during the pregnancy to check for this complication.

  • A few weeks before the due date, doctors usually deliver the baby, then remove the uterus, unless the woman objects.

When the placenta is too firmly attached, parts of the placenta may remain in the uterus after delivery. In these cases, delivery of the placenta is delayed, and the risks of bleeding and infection in the uterus are increased. Bleeding may be life threatening.

Placenta accreta is becoming more common:

  • 1950s: About 1 in 30,000 pregnancies

  • 1970s: About 1 in 4,000

  • 1980s: About1 in 2500

  • 2000s: About 1 in 250 to 500

This increase coincides with the increase in cesarean deliveries.

Risk factors

This complication is more likely to occur in women with the following characteristics:

  • Who have had a cesarean delivery

  • Whose placenta covers the cervix (called placenta previa)

  • Who are over 35

  • Who have been pregnant several times

  • Who have fibroids under the lining of the uterus (endometrium)

  • Who have had surgery involving the uterus, including removal of fibroids

  • Who have disorders of the lining of the uterus, such as Asherman syndrome (scarring of the uterine lining due to an infection or surgery)

Having had both a cesarean delivery and placenta previa in a previous pregnancy greatly increases the risk of placenta accreta in subsequent pregnancies. The more cesarean deliveries such women have had, the higher the risk.


  • Ultrasonography

  • Sometimes magnetic resonance imaging (MRI)

If a woman has conditions that increase the risk of placenta accreta, doctors usually do ultrasonography before delivery to check for placenta accreta. Ultrasonography, using a handheld device placed on the abdomen or inside the vagina, may be done periodically, starting at about 20 to 24 weeks of pregnancy. If ultrasonography is unclear, MRI may be done.

During delivery, the disorder is suspected if any of the following occur:

  • The placenta has not been delivered within 30 minutes after the baby’s delivery.

  • Doctors cannot separate the placenta from the uterus by hand.

  • Attempting to remove the placenta results in profuse bleeding.


  • Cesarean hysterectomy

If doctors detect placenta accreta before delivery, a cesarean delivery followed by removal of the uterus (cesarean hysterectomy) is typically done. For this procedure, the baby is first delivered by cesarean. Then the uterus is removed with the placenta in place. This procedure is usually done at about 34 weeks of pregnancy. It helps prevent potentially life-threatening loss of blood, which can occur when the placenta remains attached after delivery. However, the procedure can cause complications, such as profuse bleeding. Also, blood clots can develop if the surgery takes a long time and/or requires a long period of bed rest afterward. Blood clots can travel through the bloodstream and block an artery in the lungs. A cesarean hysterectomy should be done at a hospital that is equipped to handle such complications.

If future childbearing is important to the woman, doctors try to preserve the uterus using various techniques. However, these techniques cannot be used if bleeding is extremely heavy or is likely to be extremely heavy (because of the placenta's location).