Aims: To determine the incidence of postpartum diabetes mellitus in the years following a diagnosis of gestational diabetes mellitus (GDM) and to determine whether the severity of GDM, represented by the magnitude of the deviation of diagnostic tests from the normal values or requirement for medications, is associated with the development of diabetes.
Methods: A retrospective cohort study was performed among 185 416 pregnant women who had glucose challenge test or 3 h oral glucose tolerance test (OGTT) in a large health maintenance organization in Israel. Subsequent diagnosis of diabetes was ascertained by using an automated patient registry.
Results: A total of 11 270 subjects were diagnosed with GDM, comprising 6.07% of the cohort. During a total follow-up period of 1 049 334 person-years there were 1067 (16.9 per 1000 person-years) and 1125 (1.1 per 1000 person-years) diagnoses of postpartum diabetes among GDM and non-GDM women, respectively. The cumulative risk of incident diabetes in GDM patients with up to 10 years of follow-up was 15.7%, compared with 1% among the non-GDM population. Gestational diabetes mellitus was associated with nearly an eightfold higher risk of postpartum diabetes after adjusting for important confounders, such as socioeconomic status and body mass index. Among women with a history of GDM, the number of abnormal OGTT values and use of insulin were associated with a substantially higher risk for developing diabetes.
Conclusions: Three or four abnormal OGTT values and GDM requiring insulin or oral hypoglycaemic medications are important predictors of postpartum diabetes risk in women with a history of GDM.