OBJECTIVE: To study the incidence of diabetes among women with previous diet-treated gestational diabetes mellitus (GDM) in the light of the general increasing incidence of overweight and diabetes and to identify risk factors for the development of diabetes.
RESEARCH DESIGN AND METHODS: Women with diet-treated GDM during 1978-1985 (old cohort, n = 241, also followed up around 1990) or 1987-1996 (new cohort, n = 512) were examined in 2000-2002. Women were classified by a 2-h, 75-g oral glucose tolerance test according to the World Health Organization criteria or an intravenous glucagon test supplemented by measurement of GAD antibodies. Historical data from index-pregnancy and anthropometrical measurements were collected.
RESULTS: A total of 481 (63.9%) women were examined (median 9.8 years [interquartile range 6.4-17.2]) after index pregnancy. Diabetes and impaired glucose tolerance (IGT)/impaired fasting glucose were present in 40.0 and 27.0% of women, respectively. In the new cohort, 40.9% had diabetes compared with 18.3% in the old cohort at the 1990 follow-up (P < 0.0005). Prepregnancy BMI was significantly higher in the new compared with the old cohort (26.0 [22.5-30.8] vs. 22.9 kg/m2 [20.2-28.0], P < 0.0005). Among others, new-cohort membership, prepregnancy overweight (BMI > or = 25 kg/m2), and IGT postpartum were identified as independent predictors of diabetes by multiple logistic regression analyses.
CONCLUSIONS: The incidence of diabetes among Danish women with previous diet-treated GDM was very high and had more than doubled over a 10-year period. This seems to be due to a substantial increase in BMI in women with GDM.