Gestational diabetes mellitus complicated approximately 6% of pregnancies and was a major predictor of type 2 diabetes later in life. It was unclear how risk varies depending on the number of impacted pregnancies or how long the elevated risk lasts. Using a countrywide sample of 50,884 women, researchers looked at reproductive history related to type 2 diabetes risk. During the 10-year follow-up, 3,370 people who did not have diabetes at the start were diagnosed with diabetes. Investigators used Cox proportional hazards models adjusted for BMI, educational level, and race/ethnicity to determine risk based on age, the cumulative number of pregnancies with gestational diabetes mellitus, and time since the most recent affected pregnancy. With a hazard ratio of 3.87 (95% CI 2.60–5.75) 6–15 years after an affected pregnancy, a history of 1 or more pregnancies with gestational diabetes mellitus predicted an increased age-specific risk of type 2 diabetes. With many impacted pregnancies, the risk increased dramatically. After an affected pregnancy, the age-specific relationships faded with time, with an estimated 24% drop in the hazard ratio per decade. However, the risk remained elevated for more than 35 years. Type 2 diabetes was expected to be significantly higher in women with gestational diabetes mellitus. With each additional impacted pregnancy, the relative risk climbed significantly. After a pregnancy with gestational diabetes mellitus, the calculated hazard ratio decreased over time but remained increased for more than 35 years. Women who had gestational diabetes mellitus should be checked for type 2 diabetes on a regular basis, even if they were in their later years.