Obesity and the increasing odds of cesarean delivery.

Background: Knowledge of the associations between obesity and cesarean delivery (CD) is limited by previous research that does not separate the highest BMI classes.

Methods: We identified 25,604 pregnancies in retrospective electronic medical records at an inner-city academic hospital between 2000 and 2015. We examined the association between BMI at pre-pregnancy and delivery, as well as gestational weight gain (GWG), and rates of CD, gestational diabetes mellitus (GD), and pregnancy-induced hypertension (PIH) using logistic regression and chi-square.

Results: CD increased with each increase in delivery BMI class [X² (7, N = 25,604) =151.40, p < .0001]. GD and PIH also significantly increased across each BMI class. Each increasing BMI class predicted 1.21 times greater odds of CD even after adjusting for maternal age, year of birth, GD, and PIH [OR = 1.21 (95% CI, 1.07-1.37)]. As compared with the IOM recommended GWG, less weight gain offered mitigation of CD and GD, though less than the recommended GWG for women who were obese pre-pregnancy also increased odds of preterm birth, low birth weight, and stillbirth.

Conclusions: Increasing BMI is associated with increasing rates of adverse obstetric outcomes. There exists a "dose-dependent" effect of BMI on CD and limiting GWG may be associated with mitigated risk for this outcome, but increased risk for offspring adverse birth outcomes.