Our aim was to investigate whether birth weight in mothers with diabetes mellitus type 1 is higher as compared to nondiabetic controls. Methods. A retrospective study was performed using an existing database covering the region of Flanders, Belgium. Data included the presence of diabetes type 1, hypertension, parity, maternal age, the use artificial reproductive technology, fetal- neonatal death, congenital anomalies, admission to a neonatal intensive care unit, and delivery by Caesarean section or vaginally. Results. In the period studied, 354 women with diabetes type 1 gave birth and were compared with 177.471 controls. Women with type 1 diabetes more often had a maternal age of over 35 years (16.7% versus 12.0%, P = .008, OR 1.46; 95% CI 1.09-1.95). They more frequently suffered hypertension in pregnancy (19.5% versus 4.7%, P < .0001, OR 4.91; 95% CI 3.73-6.44). Perinatal death was significantly higher in the diabetes mellitus group (3.05% versus 0.73%, P < .0001, OR 4.28; 95% CI 2.22-8.01). Caesarean section was performed almost 5 times as frequently in the diabetes versus the control group (OR 4.57; 95% CI 3.70-5.65). Birth weight was significantly higher in diabetic pregnant women from 33 until 38 weeks included, but those reaching 39 weeks and later were not different with control groups. Conclusion. In Belgium, diabetic pregnancy still carries a high risk for fetal and maternal complications; in general birth weight is significantly higher but for those reaching term there is no significant difference in birth weight.