Merck Manual

Please confirm that you are not located inside the Russian Federation

honeypot link

Placenta Accreta


Julie S. Moldenhauer

, MD, Children's Hospital of Philadelphia

Last full review/revision Jan 2020| Content last modified Jan 2020
Click here for the Professional Version

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.

After delivery of the baby, the placenta usually detaches from the uterus, and the woman can push the placenta out by herself or with help from a doctor or midwife. 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. It occurred in about

  • 1 in 30,000 pregnancies in the 1950s

  • 1 in 500 to 2,000 in the 1980s and 1990s

  • 3 in 1,000 in the 2000s

This increase coincides with the increase in cesarean delivery.

Risk factors

Placenta accreta 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 a cesarean delivery in a previous pregnancy and having placenta previa in the current pregnancy greatly increases the risk of placenta accreta in subsequent pregnancies.

Diagnosis of Placenta Accreta

  • 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, placenta accreta 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.

Treatment of Placenta Accreta

  • 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).

NOTE: This is the Consumer Version. DOCTORS: Click here for the Professional Version
Click here for the Professional Version
Others also read

Also of Interest

Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID