Objective: To evaluate the relationship between weight gain and primary cesarean delivery. Methods: This was a retrospective cohort study of women 5442 who delivered a singleton from 2009-2013. Women were classified as normal weight [pre-pregnancy body mass index (BMI) 18.5 - 24.9 kg/m2], overweight (pre-pregnancy BMI 25.0 - 29.9 kg/m2), obese (pre-pregnancy BMI 30.0 - 39.9 kg/m2), and extremely obese (pre-pregnancy BMI ≥ 40.0 kg/m2). Each BMI group was subdivided by weight gain—low, recommended, or excessive, as defined by the 2009 Institute of Medicine guidelines—and rates of primary cesarean delivery were compared. Results: The overall primary cesarean delivery rate was 27.3%, but this varied based on pre-pregnancy BMI. The primary cesarean delivery rate among women of normal weight was 22.3%, overweight women 27.5%, obese women 35.3%, and extremely obese women 45.7%. Among normal-weight, obese, and extremely obese women, the risk of primary cesarean delivery increased with excessive weight gain [normal weight odds ratio (OR) 1.63, (95% confidence interval 1.32 - 2.01); obese OR 1.55 (1.12 - 2.15); extremely obese OR 2.19 (1.18 - 4.08)] compared to recommended weight gain. More than half of women (53.2%) had excessive weight gain. Conclusion: Adherence to guidelines may decrease a woman’s risk of primary cesarean delivery.