Long-term risk of type 2 diabetes mellitus in relation to BMI and weight change among women with a history of gestational diabetes mellitus: a prospective cohort study

Women with a history of gestational diabetes mellitus (GDM) are advised to control their weight after pregnancy. We aimed to examine how adiposity and weight change influence the long-term risk of developing type 2 diabetes after GDM.We included 1,695 women who had incident GDM between 1991 and 2001, as part of the DiabetesWomen's Health study, and followed them until the return of the 2009 questionnaire. Body weight and incident type 2 diabetic cases were reported biennially. We defined baseline as the questionnaire period when women reported an incident GDM pregnancy. We estimated HRs and 95% CIs using Cox proportional hazards models.We documented 259 incident cases of type 2 diabetes during up to 18 years of follow-up. The adjusted HRs of type 2 diabetes associated with each 1 kg/m(2) increase in BMI were 1.16 (95% CI 1.12, 1.19) for baseline BMI and 1.16 (95% CI 1.13, 1.20) for most recent BMI. Moreover, each 5 kg increment of weight gain after GDM development was associated with a 27% higher risk of type 2 diabetes (adjusted HR 1.27; 95% CI 1.04, 1.54). Jointly, women who had a BMI ≥30.0 kg/m(2) at baseline and gained ≥5 kg after GDM had an adjusted HR of 43.19 (95% CI 13.60, 137.11), compared with women who had a BMI25.0 kg/m(2) at baseline and gained5 kg after GDM.Baseline BMI, most recent BMI and weight gain after GDM were significantly and positively associated with risk of progression from GDM to type 2 diabetes.