OBJECTIVE: To examine the associations between gestational weight gain (GWG) exceeding Institute of Medicine (IOM) guidelines and neonatal adiposity in the five North American field centers of the Hyperglycemia and Adverse Pregnancy Outcome study. METHODS: GWG was categorized as less than, within, or greater than 2009 IOM guidelines. Birthweight, body fat percentage, cord serum C-peptide, and sum of neonatal flank, subscapular, and triceps skin fold thicknesses were dichotomized as >90th percentile or =90th percentile obtained by quantile regression. Logistic regression analysis was used. RESULTS: Of the 5297 participants, 11.6% gained less, 31.9% gained within, and 56.5% gained more than the recommendation. With adjustment for glucose tolerance levels, normal and overweight women who gained more than the recommendation had increased odds of delivering infants with sum of skin folds >90th percentile (OR = 1.75 and 4.77, respectively) and percentage body fat >90th percentile (OR = 2.41 and 2.59, respectively), and normal weight and obese women who gained more than the recommendation had increased odds of delivering infants with birthweight >90th percentile (OR = 2.80 and 1.93, respectively) compared to women who gained within the recommendation. CONCLUSIONS: This analysis showed independent associations between exceeding IOM GWG recommendations and neonatal adiposity in normal and overweight women, controlling for glucose tolerance levels.