Stillbirth Risk with Class II and III Obesity

We sought to analyze the rates of stillbirth at recommended gestational age epochs based on body mass index (BMI) at first prenatal visit. A total of 79,148 births with optimal dating, BMI at first prenatal visit, and absence of maternal complications (chronic hypertension, pregestational diabetes) or fetal complications (aneuploidy, major fetal malformations, fetal growth restriction) were identified from January 2013 to September 2024. Of these, 33,108 (42%) delivered ≥ 34 weeks with a BMI classified as normal, class II, or class III obesity. Adjusted hazard ratios (aHRs) were calculated due to differences in age, race/ethnicity, and parity. Among patients with class II obesity, no difference in stillbirth was observed compared with normal weight individuals at either early term (370/7 −386/7 weeks) or term (≥ 39 weeks), with aHRs of 2.19 (95% confidence interval [CI] 0.67–7.17) and 0.86 (95% CI 0.17–4.34), respectively. Neither were differences found in stillbirth risk for patients with class III obesity compared with normal weight individuals in the late preterm (340/7 −366/7 weeks), early term, or term gestational ages with aHRs of 0.78 (95% CI 0.17–3.57), 2.44 (95% CI 0.61–9.84), and 2.81 (95% CI 0.7–11.28), respectively. Based on our results, the utility of antepartum surveillance for the prevention of stillbirth in patients with class II or III obesity may be of limited benefit.