CONTEXT The effect of weight gain on the development of type 2 diabetes after gestational diabetes mellitus (GDM) is not fully understood in Asian women who have a relatively low body mass index (BMI).

OBJECTIVE We investigated the effect of postpartum longitudinal BMI change on the development of diabetes in Korean women with a history of GDM.

DESIGN AND SETTING The study included a hospital-based, multicenter, prospective cohort with median follow-up of 4.0 years.

PARTICIPANTS A total of 418 women with previous GDM or gestational impaired glucose tolerance were recruited and underwent an oral glucose tolerance test at 6 weeks postpartum and annually thereafter.

MAIN OUTCOME MEASURE The risk of diabetes was analyzed according to the tertiles of BMI change. Changes in BMI were calculated between the initial postpartum visit and the last follow-up or at the onset of diabetes.

RESULTS The BMI change in each tertile was -1.8 ± 1.1, -0.2 ± 0.3, and 1.6 ± 1.2 kg/m(2), respectively. We observed an increased risk of incident diabetes as the tertile of BMI change increased (8.6%, 12.6%, and 16.9%, P = .039). Postpartum BMI change was an independent predictor of diabetes in a multivariate Cox analysis (hazard ratio 1.27, 95% confidence interval 1.04-1.56, P = .021), even after adjusting for BMI at the last follow-up. In the highest tertile group, there was a significant deterioration in cardiovascular risk factors including blood pressure, lipid profile, and insulin sensitivity.

CONCLUSIONS Postpartum increase in BMI is significantly associated with a risk of diabetes and deterioration of metabolic phenotypes in Korean GDM women.