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Placenta accreta is an abnormally adherent placenta, resulting in delayed delivery of the placenta. Placental function is normal, but trophoblastic invasion extends beyond the normal boundary (called Nitabuch's layer). In such cases, manual removal of the placenta, unless scrupulously done, results in massive postpartum hemorrhage. Prenatal diagnosis is by ultrasonography. Treatment is usually with scheduled cesarean hysterectomy.
In placenta accreta, the placental villi are not contained by uterine decidual cells, as occurs normally, but extend to the myometrium. Related abnormalities include placenta increta (invasion of chorionic villi into the myometrium) and placenta percreta (penetration of chorionic villi into or through the uterine serosa). All 3 abnormalities cause similar problems.
Etiology
The main risk factor for placenta accreta is
In the US, placenta accreta most commonly occurs in women who have had placenta previa after cesarean delivery in a previous pregnancy. Incidence of placenta accreta has increased from about 1/30,000 in the 1950s to about 1/500 to 2000 in the 1980s and 1990s. Risk in women who have had placenta previa increases from about 10 to 25% if they have had one cesarean delivery to about 50 to 67% if they have had > 4 cesarean deliveries.
Other risk factors include the following:
Symptoms and Signs
Usually, women present with profuse vaginal bleeding during manual separation of the placenta after delivery of the fetus.
Diagnosis
Thorough evaluation of the uteroplacental interface by ultrasonography (transvaginal or transabdominal) is warranted in women at risk; it can be done periodically, beginning at 20 to 24 wk gestation. If ultrasonography is inconclusive, MRI or Doppler flow studies may help.
During delivery, the disorder is suspected if the placenta has not been delivered within 30 min of the infant's delivery, if no plane of separation can be created with attempts at manual removal, or if placental traction causes large-volume hemorrhage. When placenta accreta is suspected, laparotomy with preparation for large-volume hemorrhage is required.
Treatment
Preparation for delivery is best. Unless the patient objects, scheduled cesarean hysterectomy is done as soon as fetal lung maturity is confirmed (usually at about 35 to 36 wk).
If cesarean hysterectomy is done (preferably by an experienced pelvic surgeon), a fundal incision followed by immediate clamping of the cord after delivery can help minimize blood loss. The placenta is left in situ while hysterectomy is done. Balloon occlusion of the aorta or internal iliac vessels may be done preoperatively but requires a skilled angiographer and may cause serious thromboembolic complications.
Last full review/revision February 2010 by Antonette T. Dulay, MD
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