Objective: The purpose of this study was to investigate effect of increase in body mass index (BMI) category on obstetric outcomes.
Study design: A cohort study was conducted from 1999 to 2002. Women with singleton pregnancies were placed in standard BMI categories. Increase in BMI was calculated as difference between initial BMI and delivery BMI. ANOVA was used to compare continuous variables, and chi-square test for categorical variables.
Results: This study included 5131 women: 49.8% had no change in BMI category, 43.9% increased by 1 BMI category, and 6.3% by >1 category. Increase in BMI category was associated with higher rates of gestational diabetes (P = .005), failed induction (P < .001), lacerations (P < .001), cesarean deliveries (P < .001), and postpartum infection (P = .007) in normal weight women. Overweight women also had increased rates of preeclampsia (P = .002) and operative vaginal deliveries (P < .001). Obese women had higher rates of chorioamnionitis (P = .003), failed induction (P < .001), and cesarean deliveries (P = .016).
Conclusion: Increase in BMI category is associated with increased risk of complications.