Overweight and the metabolic syndrome in adult offspring of women with diet-treated gestational diabetes mellitus or type 1 diabetes Context: In animal studies exposure to intrauterine hyperglycemia increases the risk of cardiovascular disease through only partly understood epigenetic mechanisms. Human long-term follow-up studies on the same topic are few. Objective: To study the risk of overweight and the metabolic syndrome in adult offspring of women with diet-treated gestational diabetes mellitus (GDM) or type 1 diabetes, and additionally to study associations between estimates of maternal hyperglycemia and outcome in the offspring Design: Follow-up study of 1,066 primarily Caucasians aged 18-27 years. Setting: Center for pregnant women with diabetes, Rigshospitalet, Denmark Participants: Offspring of women with diet-treated GDM (n=168) and an un-exposed reference group (n=141). Offspring of women with type 1 diabetes (n=160) and offspring from the background population representing an un-exposed reference group (n=128). Follow-up rate was 56% (597/1,066). Main outcome measures: Overweight: body mass index (BMI) >/= 25kg/m(2). The metabolic syndrome: the International Diabetes Federation 2006 criteria. Results: The risk of overweight was doubled in offspring of women with diet-treated GDM or type 1 diabetes compared with offspring from the background population whereas the risk of the metabolic syndrome was four and 2.5-fold increased, respectively. Offspring risk of the metabolic syndrome increased significantly with increasing maternal fasting blood glucose as well as 2-h blood glucose (during OGTT). Conclusions: Adult offspring of women with diet-treated GDM or type 1 diabetes are risk groups for overweight and the metabolic syndrome. Intrauterine hyperglycemia may in addition to genetics and other factors contribute to the pathogenesis of overweight and the metabolic syndrome.