Observational studies suggest that minimal gestational weight gain (GWG) may optimize pregnancy outcomes for obese women. This trial tested the efficacy of a group‐based weight management intervention for limiting GWG among obese women.

One hundred and fourteen obese women (BMI [mean ± SD] 36.7 ± 4.9 kg/m²) were randomized between 7 and 21 weeks' (14.9 ± 2.6) gestation to intervention (n = 56) or usual care control conditions (n = 58). The intervention included individualized calorie goals, advice to maintain weight within 3% of randomization and follow the Dietary Approaches to Stop Hypertension dietary pattern without sodium restriction, and attendance at weekly group meetings until delivery. Control participants received one‐time dietary advice. Our three main outcomes were maternal weight change from randomization to 2 weeks postpartum and from randomization to 34 weeks gestation, and newborn large‐for‐gestational age (birth weight >90th percentile, LGA).

Intervention participants gained less weight from randomization to 34 weeks gestation (5.0 vs. 8.4 kg, mean difference = −3.4 kg, 95% CI [‐5.1‐1.8]), and from randomization to 2 weeks postpartum (−2.6 vs. +1.2 kg, mean difference = −3.8 kg, 95% CI [‐5.9‐1.7]). They also had a lower proportion of LGA babies (9 vs. 26%, odds ratio = 0.28, 95% CI [0.09‐0.84]).

The intervention resulted in lower GWG and lower prevalence of LGA newborns.