Risk factors for preterm delivery with placenta previa

Aims: To identify factors associated with preterm delivery in cases of sonographically identified placenta previa. Methods: Pregnancies with sonographic evidence of placenta previa at ≥ 28 weeks were identified. Demographic information, antepartum course, and delivery information were extracted from electronic medical records. Statistical analysis was performed with Fisher's exact test, Mann-Whitney U, Spearman' s ρ (correlation), and logistic regression. Continuous data are presented as median (interquartile range). Results: Of 113 singleton pregnancies with placenta previa, 54 (48 %) delivered at term and 59 (52 %) delivered preterm. Fifty-one (45 %) experienced antepartum bleeding at a median gestational age of 31 weeks (29 - 33 weeks) with a median interval of 20 days (11 - 33 days) between first bleeding episode and delivery. Women with antepartum bleeding were more likely to be delivered for hemorrhage (36 of 51 vs. 8 of 62, P < 0.001) and delivered emergently (40 of 51 vs. 14 of 62, P < 0.001). Antepartum bleeding before 34 weeks had a positive predictive value of 88 % for preterm birth and 83 % for emergent delivery. Conclusion: In pregnancies with placenta previa, antepartum bleeding is a strong predictor of preterm delivery.