Association of first Birth Cesarean Delivery and Placental Abruption or Previa at Second Birth

Objective: To evaluate the strength of association of cesarean delivery for first birth with placenta previa and placental abruption in second pregnancy.Design: Retrospective cohort study.Setting: Hospital based (Birth register)2004-2008. A total of 1638 pregnancies were available for the final analysis after excluding missing information.Methods: Multiple logistic regressions were used to describe the relationship between cesarean section for first birth with placenta previa and placental abruption in second birth singletons.Main outcome measures: Placenta previa and placental abruptionResults: Placenta previa was present in 10 per 1000 second-birth singletons whose first births delivered by cesarean section and 9 per 1000 second-birth singletons whose first births delivered vaginally. The corresponding figures for placental abruption were 5 per 1000 in the previous cesarean delivery group and 5 per 1000 in the previous vaginal delivery group. The adjusted odds ratio (95% confidence intervals) of previous cesarean section for placenta previa in following second pregnancies was 1.10 (0.39 to 3.10) after adjusting for confounders including maternal age and interval between births. The corresponding figure for placental abruption was 1.0 (0.24 to 4.19).Conclusion: Cesarean section for first birth is associated with 10% increased risk of placenta previa and no risk of placental abruption in second pregnancy with a singleton.