Obesity as a risk factor for cesarean in a low-risk population

To determine whether low-risk maternity patients in a nurse-midwifery service with prepregnant body mass index (BMI) above 29.0 are at increased risk for cesarean delivery.

We studied 1881 women who delivered between 1994 and 1998 and were managed by an academic inner-city hospital-certified nurse-midwifery practice. We calculated prepregnancy BMI and weight gain during pregnancy by using clinical data from a comprehensive clinical database, and did descriptive analyses and univariate and multivariate logistic regression analyses.

The overall cesarean rate was 5.1%, but was 7.7% for obese women compared with 4.1% for women with normal BMI (19.8-25.9). The unadjusted odds ratio (OR) for cesarean for obese women was 2.02 (95% confidence interval [CI] 1.26, 3.25, P <.01). Other factors associated with increased risk of cesarean delivery included primigravidity, primiparity, maternal age 35 years or older, short stature (height under 155 cm), very low birth weight infant, failure to progress, breech presentation, abruption, fetal bradycardia, and severe preeclampsia. Maternal race and marital status were not associated with cesarean delivery. After adjustment for weight gain, short stature, advanced maternal age, primiparity, and intrapartum complications, the OR for obesity was 3.99 (95% CI 2.00, 7.95, P <.001).

Even among low-risk women managed by nurse-midwives, the risk of cesarean delivery was higher for obese women. Short, obese women were at higher risk of cesarean delivery compared with women with normal BMIs, but were not high enough risk to preclude them from receiving nurse-midwifery care.