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.