Poor glycemic control in early pregnancy in insulin-dependent diabetes is associated with an increased risk for spontaneous abortions and congenital malformations. Strict glycemic control from the initial stages of embryogenesis is one of the major goals of management in these pregnancies. We hypothesized that insulin-dependent diabetic patients attending a pre-conception program would have improved glycemic control compared with insulin-dependent diabetic patients who enrolled after conception and would have better pregnancy outcome, with fewer spontaneous abortions and fewer major malformations. Ninety-nine pregnant insulin-dependent diabetic patients were recruited before reaching 9 weeks' gestation and were followed prospectively throughout pregnancy. Twenty-eight had attended a pre-conception clinic to optimize glycemic control (study group) and 71 had enrolled after conception (control group). Early glycemic control was significantly better in the study group: Glycohemoglobin values at the first prenatal visit and at 9 and 14 weeks' gestation were significantly lower than in the control group. The rate of spontaneous abortion was significantly lower in the study group (7%) than in the controls (24%). There was one major malformation in the control group and none in the study group. We conclude that patients with insulin-dependent diabetes attending a pre-conception program have a decreased rate of early pregnancy loss compared with those receiving prenatal care early in pregnancy.