Analysis of the predictable variables for placenta accreta without placenta previa

Objectives To clarify the predictive variables for adherence of the placenta (AP) in cases without placenta previa. Methods A prospective cohort study was conducted between 2008 and 2010. Patients without placenta previa who delivered singleton babies after 36 weeks' gestation were enrolled. The maternal and ultrasonographic variables associated with AP were evaluated at the time of admission for delivery. Results A total of 2834 consecutive subjects were included. Placenta accreta without placenta previa was observed in six cases (0.2 %). Two cases in which the placenta was located on the previous uterine scar had AP, but AP was found only in 0.1 % of cases in which the placenta was not on the previous scar (p < 0.001). AP was frequently observed in cases with a history of previous uterine surgery compared to cases without a history [(1.9 vs. 0.1 %) p < 0.001]. AP was observed in 33 % of cases in which no retroplacental clear zone was detected, whereas AP was observed in only 0.1 % of cases with a clear zone (p < 0.001). Conclusion A past history of uterine surgery, ultrasonographic findings of no retroplacental clear zone, and a placenta on the uterine scar were associated with AP in cases without placenta previa.