Forty-four of 75 pregnant women with juvenile-onset insulin-dependent diabetes, who attended a preconceptional clinic, were seen regularly by a diabetologic team. Glycemic control was obtained by intensified insulin therapy and monitored by blood glucose self-monitoring. When these patients were compared with a group of 31 nonattenders of the preconceptional clinic, in the former normoglycemia and normal hemoglobin A1 values were achieved before conception, whereas in the latter good control was reached by the second trimester. This group had also more maternal complications, such as preeclampsia, and higher cesarean section rates. Congenital anomalies were 9.6% among offspring of nonattenders, while none occurred in those with preconceptional counseling. We confirm the evidence accumulated in the recent literature that congenital malformations in pregnancy complicated by diabetes may be linked to disturbances in maternal metabolism during the period of embryogenesis. Consequently we concur with the recommendation that tight diabetic control is required before the patient attempts to conceive.