468: Does the presence of placental basal plate myometrial fibers in a prior pregnancy improve prediction of placenta accreta?

Abstract

Antenatal diagnosis of accreta has been shown to improve outcome, but existing predictors lack sensitivity. Our objective was to determine whether the presence of myometrial fibers attached to the placental basal plate (BPMYO) in an antecedent pregnancy predicts subsequent placenta accreta. This is a case-control study of women who had at least two pregnancies with placental pathologic evaluation at Northwestern University. Cases were defined as women with evidence of accreta (both clinically and pathologically) while women without evidence of accreta served as controls. Pathologic specimens from placentas from prior pregnancies of the study group were evaluated for BPMYO. The presence of BPMYO on a prior placenta was incorporated with established predictors of accreta to evaluate changes in the testing characteristics of antenatal diagnosis of accreta. Of the 25 cases of placenta accreta, 19 (76%) had BPMYO present on their prior placenta compared to 41 (40%) of controls (OR=4.8, 95% CI 1.8-13.0). Adding BPMYO to a regression including other established risk factors for accreta (i.e., maternal age, number of prior cesareans, previa, any prior curettage, and ultrasonographic suspicion of accreta) significantly improved the sensitivity of antenatal diagnosis of accreta without an adverse effect on specificity (Table). The finding of BPMYO on prior placental pathology may improve the ability to antenatally detect a placenta accreta when used in combination with other known risk factors for accreta.