Early Pregnancy Body Roundness Index and Development of Adverse Pregnancy Outcomes: A Secondary Analysis of the nuMoM2b Study.

OBJECTIVE: This study assessed the association between early pregnancy body roundness index (BRI) and adverse pregnancy outcomes in nulliparas. METHODS: In this secondary analysis of a multicenter prospective cohort study, waist circumference, height, and weight were measured between 6 and 13 6/7 weeks' gestation and used to calculate BMI and BRI (364.2-365.5 × {1 - [(waist circumference/2π)/(0.5 × height)]2}0.5). Four BRI and BMI quantiles (Q1-Q4) were defined, and rates of adverse pregnancy outcomes were compared using multivariable logistic regression. RESULTS: Among 9671 individuals, greater BRI was associated with gestational diabetes (GDM), hypertensive disorders, preterm birth, cesarean delivery, and large-for-gestational age infants. Discordant BRI and BMI assignments affected GDM and cesarean odds. Those with Q2 BMI but Q3-Q4 BRI had increased odds of GDM (aOR 2.28, 1.49-3.47) and cesarean (aOR 1.39, 1.15-1.68). Those with Q3 BMI and Q1-Q2 BRI demonstrated reduced odds for GDM (aOR 0.31, 0.15-0.63) and cesarean (aOR 0.75, 0.60-0.94). Participants with Q4 BMI and Q1-Q3 BRI experienced decreased odds for cesarean (aOR 0.55, 0.43-0.70) but similar GDM odds. CONCLUSIONS: Greater first trimester BRI, a reflection of central adiposity, is associated with adverse pregnancy outcomes. Early pregnancy BRI may improve risk stratification for GDM and cesarean delivery beyond BMI.