A population-based birth cohort including 296 consecutive type 1 diabetic births in a geographically defined catchment area was used to evaluate factors predicting poor perinatal and neonatal outcome. Though perinatal mortality has decreased (17.1/1000 births at 28 or more weeks of gestation), the neonatal morbidity rate still remains high despite improved maternal metabolic control and developed antepartum surveillance. Poor glycemic control during the first weeks of pregnancy was the most important risk factor (relative risk (RR) 2.91; 95% confidence interval (CI) 1.29-6.55) predicting adverse neonatal events such as long (>10 days) stay in the neonatal unit, malformation or perinatal death. The risk was further increased in cases of severe diabetes (White class F-R; RR 2.75; 95% CI 1.59-4.76) and primiparity (RR 1.64; 95% CI 1.02-2.65). By evaluating these risk factors at the first antenatal visit, a subgroup with a particular need of counselling and intensive feto-maternal monitoring can be identified.