Placenta accreta: risk factors, perinatal outcomes, and consequences for subsequent births

We sought to evaluate risk factors and perinatal outcomes of pregnancies complicated with placenta accreta and to study perinatal outcomes in subsequent pregnancies.

A retrospective study comparing all singleton cesarean deliveries (CD) of women with and without placenta accreta was conducted. In addition, a retrospective comparison of all subsequent singleton CD of women with a previous placenta accreta, with CD of women with no such history, was performed during the years 1988 through 2011. Stratified analysis using multiple logistic regression models was performed to control for confounders.

During the study period, there were 34,869 CD, of which 0.4% (n = 139) were complicated with placenta accreta. Using a multivariable analysis with backward elimination, year of birth (adjusted odds ratio [aOR], 1.06; 95% confidence interval [CI], 1.03-1.09; P < .001), previous CD (aOR, 5.11; 95% CI, 3.42-7.65; P < .001), and placenta previa (aOR, 50.75; 95% CI, 35.57-72.45; P < .001) were found to be independently associated with placenta accreta. There were 30 subsequent pregnancies of women with placenta accreta. Recurrent accreta occurred in 4 patients (13.3%). Previous placenta accreta was significantly associated with uterine rupture (3.3% vs 0.3%, P < .01) peripartum hysterectomy (3.3% vs 0.2%, P < .001), and the need for blood transfusions (16.7% vs 4%, P < .001). Nevertheless, increased risk for adverse perinatal outcomes such as low Apgar scores at 1 and 5 minutes and perinatal mortality was not found in these patients.

Prior CD and placenta previa are independent risk factors for placenta accreta. A pregnancy following a previous placenta accreta is at increased risk for adverse maternal outcomes such as recurrent accreta, uterine rupture, and peripartum hysterectomy. However, adverse perinatal outcomes were not demonstrated.