Blood lactate levels were determined by Lactate Analyzer 640 Kontron in 5 infants of diabetic mothers with pregestational insulin-dependent-diabetes, class B-C-D White, BPSP negative, in strict glycemic control all along the pregnancy. In the mothers blood lactate was found in a normal range after-delivery. In the absence of complications, the neonate of diabetic mother did not show blood lactate changes above the normal range. As well as in the neonate of non diabetic mother, blood lactate increases were found only in concomitance with respiratory acidosis. In the cases with favourable course, lactate values above 2 mmol/l were normalized in the first 24 hours after the birth. The semiautomatic determination of blood lactate supplies a good prognostic evaluation of the association between metabolic and respiratory acidosis in the neonate and should therefore be routinely used in centers for management of diabetic pregnancy.