Maternal body mass index, delivery route, and induction of labor in a midwifery caseload.

The purpose of this study was to identify the association between prepregnancy body mass index (BMI), weight gain in pregnancy, and newborn birth weight on route of delivery and induction of labor in patients receiving nurse-midwifery care. This retrospective cohort study examined the outcomes of 1500 consecutively delivered women who were cared for by two midwifery practices and delivered between January 1, 1998, and December 31, 2000. Cesarean delivery was significantly associated with the obese BMI (P < .001), nulliparity (P < .02), and newborn birth weight (P =.006). Prenatal weight gain did not have a significant correlation with cesarean birth (P = .24). In multivariable modeling, obese BMI, high newborn birth weight, nulliparity, and induction of labor increased the risk of cesarean birth. There was also a significant association between higher BMI and risk of induction of labor (P < .001). In a secondary analysis, obese BMI was associated with increased risk of induction in cases with ruptured membranes (OR 2.2; 95% CI 1.4-3.4) and postdates pregnancy (OR 2.0; 95% CI 1.1-3.4).