The Influence of Obesity and Diabetes on the Risk of Cesarean Delivery

Ehrenberg HM, Durnwald CP, Catalano P, Mercer BM. Am J Obstet Gynecol. 2004;191:969-974.

Pregravid obesity is a strong independent influence on route of delivery, with the risk of cesarean delivery increasing with increasing body mass index (BMI), as demonstrated in this large cohort study. Records of 12,303 singleton deliveries were evaluated; 14.0% of women were underweight (BMI<19.8 kg/m²), 42.8% were of normal weight (19.8 to 25.0 kg/m²), 21.2% were overweight (25.1 to 30.0 kg/m²), and 22.9% were obese (>30 kg/m²). Of all deliveries, 9.6% were by cesarean section.

Obesity was found to be a risk factor for cesarean delivery, independent of diabetes, macrosomia, nulliparity, or induction. The rate of cesarean delivery was higher in obese (13.8%) and overweight (10.4%) women compared with women of normal weight (7.7%; P<.0001). The risk of cesarean delivery increased with increasing BMI; the odds ratio for cesarean delivery was 1.5 in overweight women (95% CI: 1.3–1.8) and 2.4 in obese women (95% CI: 2.0,2.9; P<.0001 for each), compared with woman of normal weight. Additional risk factors for cesarean delivery were macrosomia, nulliparity, induction, diabetes, and black ethnicity.

Estimates of the prevalence of obesity in pregnant women in the US range from 18.5% to 38.3%, and it has been reported that one-third of women are ≥200 pounds at time of delivery. The results of this study show that obesity significantly affects route of delivery in pregnancy and should be taken into consideration when counseling overweight or obese women who are trying to conceive.