Congenital anomalies in newborns of women with type 1 diabetes: nationwide population-based study in Norway, 1999-2004

Objective. To estimate the risk of congenital anomalies in offspring of women with type 1 diabetes in Norway during recent years. Design. Nationwide population-based study using the Medical Birth Registry of Norway and the Norwegian type 1 Diabetes Registry. Setting. All birth clinics in Norway. Participants. All births in Norway during 19992004 (N = 350,961), of which 1,583 were births by a mother registered with pregestational type 1 diabetes. Main outcome measure. Congenital anomalies, excluding minor anomalies according to the EUROCAT system. Results. Anomalies were registered in 5.7% of offspring of women with type 1 diabetes, and in 2.9% among the background population (odds ratio 2.1, 95% CI: 1.7-2.6). Cardiovascular anomalies were registered in 3.2% in the diabetes group and 0.94% in the background population (odds ratio 3.5, 95% CI: 2.7-4.7). Results were similar when restricted to women identified with type 1 diabetes through the Diabetes Registry. Conclusions. Women in Norway with type 1 diabetes experience a significantly higher risk of congenital anomalies in their babies compared with the background population.