Placenta previa in the second trimester: sonographic and clinical factors associated with its resolution.

We identify characteristics that predict resolution of placenta previa and develop a clinical model for likelihood of resolution. We conducted a retrospective study of 366 singleton pregnancies complicated by placenta previa diagnosed with resolution of the previa as the primary outcome. Regression analyses were performed to determine variables associated with resolution and optimal timing for repeat sonographic evaluation. A likelihood of resolution model was created using a parametric survival model with Weibull hazard function. Of the 366 cases, 84% of complete placentae previae and 98% of marginal placentae previae resolved at a mean gestational age of 28.6 ± 5.3 weeks. Only gestational age and distance from the internal cervical os at the time of diagnosis were significantly associated with resolution ( P < 0.01). Likelihood of resolution was not significantly associated with any other variables. Marginal previae diagnosed in the second trimester do not appear to warrant repeat ultrasound evaluation for resolution. © Thieme Medical Publishers.