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Am Fam Physician. 1999;60(2):636

In placenta accreta, the anchoring placental villi directly contact the myometrium, leading to incomplete separation at the time of delivery. The most significant complication of placenta accreta is postpartum hemorrhage; it is reported to have a mortality rate of around 7 percent and is the most common indication for birth-related hysterectomy. According to a review by Resnik, the incidence of placenta accreta is rising, and physicians need to be aware of the condition, particularly in women with a history of previous cesarean delivery or another source of uterine scarring.

Although many cases are not reported, placenta accreta may occur in approximately one of every 2,500 pregnancies. In cases of placenta previa, the risk of accreta is 1 to 5 percent. In women with a history of one cesarean delivery, the incidence of placenta accreta may be as high as 30 percent. The risk increases with multiple cesarean deliveries and is also increased in women with a history of uterine surgeries or maternal age over 35 years. Women with risk factors should be screened for placenta accreta by ultrasound examination or colorflow Doppler studies. The role of magnetic resonance imaging in diagnosing placenta accreta has not yet been established; however, it frequently confirms or rules out a diagnosis when ultrasound results are uncertain. Placenta accreta should also be suspected when the maternal alpha-fetoprotein level is elevated during the second trimester, there is no fetal abnormality or reason to suspect other causes of elevated alpha-fetoprotein levels, and the placenta is low-lying.

The management of placenta accreta depends on control of hemorrhage. If the condition is diagnosed before labor, the delivery should be scheduled so that adequate blood replacement can be provided and cesarean hysterectomy performed, if necessary. In cases of severe bleeding related to placenta accreta following vaginal delivery, selective embolization of pelvic blood vessels and balloon occlusion of the aorta or hypogastric vessels have been attempted to control hemorrhage without resorting to hysterectomy. An alternative but unsubstantiated treatment is to leave the placenta undelivered and treat the patient with methotrexate.

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