Intensive treatment of insulin-dependent diabetes mellitus during pregnancy often normalizes plasma glucose levels. However, it is unclear whether this adversely affects other metabolic fuels that are essential to normal fetal growth and development. Metabolic studies were conducted after the subjects ingested a standardized mixed meal during each trimester in 7 normal and 15 insulin-dependent diabetic pregnant women. The latter were treated with continuous subcutaneous insulin infusion or multiple injections, which were adjusted to achieve strict glucose control throughout pregnancy. Insulin, alanine, branched-chain amino acids, triglycerides, free fatty acids, and ketones were measured every 15 to 30 minutes before a standardized breakfast and for 150 minutes after the breakfast. Patients with insulin-dependent diabetes mellitus were studied while they received their unusual insulin dosages. Fasting glucose levels (87 +/- 7 mg/dl) and glucose levels 150 minutes after the meal (112 +/- 11 mg/dl) were near normal. However, normoglycemia was achieved at the expense of increased plasma insulin levels (area under insulin response curves, p less than 0.01, vs nondiabetic curves). Nevertheless, fasting and post-prandial plasma branched-chain amino acids, alanine, and free fatty acids were similar in both groups. Fasting cholesterol, triglyceride, and ketone levels were also normalized. We conclude that normalization of circulating amino acids and lipids in conjunction with correction of hyperglycemia may contribute to favorable outcomes in infants of intensively treated diabetic mothers.