Placenta accreta and the risk of adverse maternal and neonatal outcomes

Placenta accreta is an increasingly prevalent and potentially dangerous complication of pregnancy. Although most studies on the subject have addressed the risk factors for the development of this condition, evidence on maternal and neonatal outcomes for these pregnancies is scarce. The objective of the present study is to compile current evidence with regard to risk factors as well as adverse outcomes associated with placenta accreta.

We conducted a complete literature review using PubMed, MEDLINE, Cochrane Database Reviews, UptoDate, DocGuide, as well as Google scholar and textbook literature for all articles on placenta accreta, and any one of the following keywords: "risk factors", "maternal outcomes", "neonatal outcomes", "morbidity", and "mortality". Individual case reports were excluded.

We reviewed 34 studies conducted between 1977 and 2012. A total number of 508,617 deliveries were studied, with 865 cases of confirmed placenta accreta (average pooled incidence = 1/588). The development of placenta accreta appears to be most strongly predicted by a history of cesarean section, low-lying placenta/previa, in vitro fertilization pregnancy, as well as elevated second-trimester levels of α-fetoprotein and β-human chorionic gonadotropin. The most significant maternal outcomes include the need for postpartum transfusion due to hemorrhage and peripartum hysterectomy. Maternal mortality remains rare but significantly higher than among matched, postpartum controls. Important neonatal outcomes include preterm birth, low birth weight, small for gestational age, and reduced 5-min Apgar scores. Whether the need for neonatal intensive care unit admission and steroid administration is iatrogenic and whether an increased risk of perinatal mortality is a clinically significant and independent outcome remain controversial.

Although there is a significant shortage of studies on the subject, it appears that placenta accreta is associated with adverse maternal and neonatal outcomes, some of which may be life threatening. Prenatal diagnosis and adequate planning, particularly in high-risk populations, may be indicated for the reduction of these adverse outcomes.