The maternal body mass index: a strong association with delivery route

Objective: We sought to assess body mass index (BMI) effect on cesarean risk during labor.

Study design: The Consortium on Safe Labor collected electronic data from 228,668 deliveries. Women with singletons > or = 37 weeks and known BMI at labor admission were analyzed in this cohort study. Regression analysis generated relative risks for cesarean stratifying for parity and prior cesarean while controlling for covariates.

Results: Of the 124,389 women, 14.0% had cesareans. Cesareans increased with increasing BMI for nulliparas and multiparas with and without a prior cesarean. Repeat cesareans were performed in > 50% of laboring women with a BMI > 40 kg/m(2). The risk for cesarean increased as BMI increased for all subgroups, P < .001. The risk for cesarean increased by 5%, 2%, and 5% for nulliparas and multiparas with and without a prior cesarean, respectively, for each 1-kg/m(2) increase in BMI.

Conclusion: Admission BMI is significantly associated with delivery route in term laboring women. Parity and prior cesarean are other important predictors.