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
From 1998 to 2011 in the United States, 1 in 272
This increase coincides with the increase in cesarean delivery Cesarean Delivery Cesarean delivery is surgical delivery of a baby by incision through a woman’s abdomen and uterus. In the United States, up to 30% of deliveries are cesarean. Doctors use a cesarean delivery... read more 
.
Risk factors
Placenta accreta is more likely to occur in women with the following characteristics:
Who have had a cesarean delivery
Who are over 35
Who have been pregnant several times
Who have fibroids Fibroids A fibroid is a noncancerous tumor composed of muscle and fibrous tissue. It is located in the uterus. Fibroids can cause pain, abnormal vaginal bleeding, constipation, repeated miscarriages... read more
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 Blood clots Staying in bed for a long time without regular physical activity, as may occur in a hospital, can cause many problems. (See also Problems Due to Hospitalization.) A leg injury, leg surgery,... read more 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 by an experienced surgeon and at a hospital that is equipped to handle the 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).
