Risk factors and perinatal outcomes for persistent placenta previa in nulliparas

BACKGROUNDPlacenta previa diagnosed on midtrimester ultrasound often resolves by the third trimester. Multiparity and previous cesarean delivery have been associated with persistence of placenta previa at delivery. Risk factors for persistent placenta previa in nulliparas are not well characterized. OBJECTIVEThis study aimed to identify risk factors for persistent placenta previa in the nulliparous population, and evaluate differences in outcomes between persistent and resolved placenta previa. STUDY DESIGNThis was a secondary analysis of the Nulliparous Pregnancy Outcomes Study: Monitoring Mothers-to-be (nuMoM2b), a prospective cohort study that observed 10,037 nulliparous individuals throughout pregnancy. Nulliparas diagnosed with placenta previa on midtrimester ultrasound were included in this analysis. Baseline characteristics and delivery outcomes of nulliparas with persistent placenta previa were compared with those of nulliparas with resolved placenta previa. Multivariate logistic regression with stepwise model selection was used for adjusted analyses. RESULTSA total of 171 nulliparas (1.7%) in the nuMoM2b study were diagnosed with placenta previa on midtrimester ultrasound, of whom 17% (n=29) had persistent placenta previa at delivery. When compared with those with resolved placenta previa, nulliparas with persistent placenta previa were more likely to be older (median, 32 years [interquartile range, 30-37] vs 29 years [interquartile range, 25-31]; P