Increasing Incidence of Diabetes After Gestational Diabetes

Abstract

Women with gestational diabetes mellitus (GDM) are known to be at increased risk of having overt diabetes, especially type 2 diabetes, later in life. Most long-term studies, however, involved non-European populations and did not distinguish between dietary and insulin treatment. The investigators determined the long-term risk of diabetes in Danish women having diet-treated GDM. An “old” cohort of 241 women presented in 1978–1985 and followed up for 2 to 11 years. A “new” cohort of 512 women presented at the same center in 1987–1996 and were reassessed in 2000–2002. The oral glucose tolerance test, done using 50 or 75 g of glucose, was read as abnormal if at least 2 of 7 blood glucose values exceeded 3 standard deviations above the mean for nonpregnant women. A total of 481 women, nearly two thirds of the total, were followed up a median of 9.8 years after the index pregnancy. Diabetes was present at follow up in 40% of women and impaired glucose tolerance or impaired fasting glucose in 27%. Type 2 diabetes was diagnosed in 171 of 192 patients affected. All 12 women with overt diabetes in the postpartum period had diabetes at follow up. The incidence of diabetes was more than 2-fold higher in the new cohort than in the old one in 1990, but rates were similar at follow up in 2002. On multiple logistic regression analysis, diabetes was independently associated with being in the new cohort, overweight or obesity before pregnancy, an early diagnosis of GDM, a high fasting glucose at the time of oral glucose tolerance testing, and impaired glucose tolerance in the postpartum period. This study demonstrated a doubling in the incidence of diabetes and impaired glucose tolerance or impaired fasting glucose over a 10-year period in women having diet-treated GDM. Prepregnancy obesity further increased the risk, suggesting that timely intervention might prevent or delay the development of overt diabetes.