Diabetes mellitus following gestational diabetes: role of subsequent pregnancy

Objective This study was designed to determine the rate of diabetes up to 13 years after pregnancies complicated by gestational diabetes and to identify risk factors for developing diabetes. The role of a subsequent pregnancy, with and without gestational diabetes, was also examined. Design This was a retrospective cohort study of women with gestational diabetes. Population and setting Women who had gestational diabetes in their first pregnancy between 1989 and 2002 were identified through a population-based perinatal database in Nova Scotia, Canada. Methods Subsequent diagnoses of diabetes, up to 13 years after the first pregnancy, were obtained from physician billing and hospital discharge databases. Cox proportional hazards regression models were used to estimate adjusted relative risks (RR) and 95% confidence intervals. Main outcome measures Diagnosis of diabetes after pregnancy. Results Of the 1401 nulliparous women with gestational diabetes, 251 women (17.9%) developed diabetes in the follow-up period. The cumulative incidence at 1, 5, and 10 years was 5.9, 14.8, and 22.2%, respectively. Factors significantly associated with an increased risk of developing diabetes mellitus included a pre-pregnancy weight of >= 86 kg (RR = 1.8, 95% CI 1.2-2.9), insulin therapy during the index pregnancy (RR = 4.1, 95% CI 2.1-7.9), neonatal hypoglycaemia (RR = 2.6, 95% CI 1.6-4.2), and a subsequent pregnancy with gestational diabetes (RR = 2.3, 95% CI 1.6-3.4). Conclusion Indicators of the severity of gestational diabetes, defined by insulin use, neonatal hypoglycaemia, and recurrent gestational diabetes in a subsequent pregnancy, are important in predicting a subsequent diagnosis of diabetes. Our findings do not support the theory that subsequent pregnancy, per se, increases the risk of developing diabetes.