The Relative Contribution of Prepregnancy Overweight and Obesity, Gestational Weight Gain, and IADPSG-Defined Gestational Diabetes Mellitus to Fetal Overgrowth

OBJECTIVE The International Association of Diabetes in Pregnancy Study Groups (IADPSG) criteria for diagnosis of gestational diabetes mellitus (GDM) identifies women and infants at risk for adverse outcomes, which are also strongly associated with maternal overweight, obesity, and excess gestational weight gain. RESEARCH DESIGN AND METHODS We conducted a retrospective study of 9,835 women who delivered at ≥20 weeks' gestation; had a prenatal, 2-h, 75-g oral glucose tolerance test; and were not treated with diet, exercise, or antidiabetic medications during pregnancy. Women were classified as having GDM based on IADPSG criteria and were categorized into six mutually exclusive prepregnancy BMI/GDM groups: normal weight ± GDM, overweight ± GDM, and obese ± GDM. RESULTS Overall, 5,851 (59.5%) women were overweight or obese and 1,892 (19.2%) had GDM. Of those with GDM, 1,443 (76.3%) were overweight or obese. The prevalence of large-for-gestational-age (LGA) infants was significantly higher for overweight and obese women without GDM compared with their normal-weight counterparts. Among women without GDM, 21.6% of LGA infants were attributable to maternal overweight and obesity, and the combination of being overweight or obese and having GDM accounted for 23.3% of LGA infants. Increasing gestational weight gain was associated with a higher prevalence of LGA in all groups. CONCLUSIONS Prepregnancy overweight and obesity account for a high proportion of LGA, even in the absence of GDM. Interventions that focus on maternal overweight/obesity and gestational weight gain, regardless of GDM status, have the potential to reach far more women at risk for having an LGA infant.