Extreme morbid obesity and labor outcome in nulliparous women at term

We examined the prevalence of cesarean delivery (CD) among women with morbid obesity and extreme morbid obesity. Using Kentucky birth certificate data, a cross-sectional analysis of nulliparous singleton gestations at term was performed. We examined the prevalence of CD by body mass index (BMI; in kg/m ²) using the National Institutes of Health/World Health Organization schema and a modified schema that separates extreme morbid obesity (BMI 50) from morbid obesity (BMI 40 to <50). Bivariate and multivariate analyses were performed. Multivariate modeling controlled for maternal age, estimated gestational age, birth weight, diabetes, and hypertensive disorders. Overall, 83,278 deliveries were analyzed. CD was most common among women with a prepregnancy BMI 50 (56.1%, 95% confidence interval 50.9 to 61.4%). Extreme morbid obesity was most strongly associated with CD (adjusted odds ratio 4.99, 95% confidence interval 4.00 to 6.22). Labor augmentation decreased the likelihood of CD among women with extreme morbid obesity, but this failed to reach statistical significance. We speculate a qualitative or quantitative deficiency in the hormonal regulation of labor exists in the morbidly obese parturient. More research is needed to better understand the influence of morbid obesity on labor.