Gestational Age, Infant Birth Weight, and Subsequent Risk of Type 2 Diabetes in Mothers: Nurses' Health Study II

Introduction Women with a history of gestational diabetes mellitus (GDM) are at higher risk of developing type 2 diabetes (T2DM); however, little is known about the association between other common pregnancy complications (eg, preterm birth, macrosomia) and T2DM risk. We examined the associations between first-pregnancy preterm, postterm birth, low birth weight, and macrosomia with subsequent risk of T2DM. Methods We conducted a prospective cohort study of Nurses' Health Study II (NHSII) participants; 51,728 women in the study had a single live birth and complete pregnancy history. NHSII confirmed incident diabetes mellitus through supplemental questionnaires. Participants were followed from year of first birth until 2005. We defined gestational age as very preterm (20 to <= 32 weeks), moderate preterm (33 to <= 37 weeks), term (38 to <= 42 weeks), and postterm (>= 43 weeks). We defined low birth weight as an infant born at term weighing less than 5.5 pounds, and we defined macrosomia as an infant born at term weighing 10 pounds or more. We used Cox proportional hazards models, adjusting for potential confounders. Results Women with a very preterm birth (2%) had an increased T2DM risk (adjusted hazard ratio, 1.34; 95% confidence interval [CI], 1.05-1.71). This increased risk emerged in the decade following pregnancy. Macrosomia (1.5%) was associated with a 1.61 increased T2DM risk, after adjusting for risk factors, including GDM (95% CI, 1.24-2.08). This association was apparent within the first 5 years after pregnancy. Moderate preterm and term low birth weight did not significantly increase the risk of T2DM over the 35-year follow-up time. Conclusion Women who experienced a very preterm birth or had an infant that weighed 10 pounds or more may benefit from lifestyle intervention to reduce T2DM risk. If replicated, these findings could lead to a reduced risk of T2DM through improved primary care for women experiencing a preterm birth or an infant of nonnormal birth weight.