Persistence of Risk for Type 2 Diabetes After Gestational Diabetes Mellitus

OBJECTIVE: Gestational diabetes mellitus complicates ∼6% of pregnancies and strongly predicts subsequent type 2 diabetes. It has not been fully elucidated how risk depends on the number of affected pregnancies or how long the excess risk persists. RESEARCH DESIGN AND METHODS: We assessed reproductive histories in relation to risk of type 2 diabetes using a nationwide cohort of 50,884 women. Among participants who initially did not have diabetes, 3,370 were diagnosed with diabetes during 10 years of follow-up. We used Cox proportional hazards models that allowed risk to depend on age, cumulative number of pregnancies with gestational diabetes mellitus, and time since the most recent affected pregnancy, adjusting for BMI, educational level, and race/ethnicity. RESULTS: History of one or more pregnancies with gestational diabetes mellitus predicted elevated age-specific risk of type 2 diabetes, with a hazard ratio of 3.87 (95% CI 2.60–5.75) 6–15 years after an affected pregnancy. Risk increased steeply with multiple affected pregnancies. The age-specific associations attenuated over time after an affected pregnancy, with an estimated 24% reduction of the hazard ratio per decade. Risk remained elevated, however, for >35 years. CONCLUSIONS: Gestational diabetes mellitus predicted markedly increased rates of type 2 diabetes. Relative risk increased substantially with each additional affected pregnancy. The estimated hazard ratio declined with time after a pregnancy with gestational diabetes mellitus but remained elevated for >35 years. Women recalling a history of gestational diabetes mellitus should be screened regularly for type 2 diabetes, even late in life.