Placenta previa and prior cesarean delivery: how strong is the association?

ABSTRACT

OBJECTIVE: To investigate the occurrence of placenta previa following a cesarean delivery. METHODS: We conducted a case-control study using 1984-1987 Washington state birth certificate data. Analysis was restricted to women who reported one or more previous live births. The study population included 490 women with a pregnancy complicated by placenta previa and 1477 randomly selected controls. Unconditional logistic regression was used for statistical analysis. RESULTS: After adjustment for confounding factors, the odds ratio for placenta previa in association with one or more previous cesarean deliveries was 1.48 (95% confidence interval 1.13-1.95). CONCLUSIONS: Women with a history of cesarean delivery are 50% more likely to have a subsequent birth complicated by placenta previa than those without such a history. This magnitude of excess risk is lower than the relative risks reported in previous studies.