Association of Gestational Weight Gain with Adverse Pregnancy Outcomes in Individuals with Obesity.

This study aimed to determine optimal gestational weight gain (GWG) considering adverse infant and maternal outcomes among individuals with obesity, with detailed classification for body mass index (BMI) of 40 kg/m² or higher.This study was a population-based retrospective cohort study, using U.S. birth certificate data from 2017 to 2021. We included nulliparous individuals with singleton pregnancies delivering live births between 37^0/7 and 41^6/7 weeks' gestation, excluding those with pregestational diabetes or hypertension, gestational diabetes, preeclampsia, major fetal anomalies, or chromosomal disorders. The study focused on three main outcomes: primary cesarean delivery, small for gestational age (SGA), and large for gestational age (LGA). GWG was evaluated in 2-kg increments, from weight loss >8 kg to gains ≥28 kg. Prepregnancy BMI was stratified into four categories: BMI of 30 to <35, 35 to <40, 40 to <50, and ≥50 kg/m². Odds ratios and absolute risk reduction were used to identify GWG ranges with balanced risks for three outcomes within each BMI category.Among 1,677,968 individuals with obesity, increased GWG was associated with higher absolute risks of cesarean delivery and LGA and lower risk of SGA across all BMI categories. Optimal GWG ranges varied by prepregnancy BMI: >12 to ≤14 kg for BMI of 30 to <35 kg/m²; >10 to ≤12 kg for BMI of 35 to <40 kg/m²; >6 to ≤10 kg for BMI of 40 to <50 kg/m²; >0 to ≤8 kg for BMI of 50 kg/m² or higher.We identified higher upper and lower GWG limits for individuals with BMI of 30 to 50 kg/m², and lower limits for those with BMI ≥50 kg/m², compared with the guidelines recommended by the U.S. National Academy of Medicine. These findings suggest the need to tailor GWG recommendations based on the severity of obesity. · Optimal GWG varies by obesity class, requiring tailored guidelines.. · Those with BMI ≥50 kg/m may need lower target for gestational gain than current recommendation.. · The optimal GWG range could be changed based on the outcomes of interest..