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

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.