Metabolism during normal and diabetic pregnancy and its effect on neonatal outcome.

Diurnal profile studies have been used to define the fetal carbohydrate and lipid substrate environment in normal and diabetic women during late pregnancy. In women with normal glucose tolerance the diurnal plasma glucose concentration was maintained within close limits (mean +/- S.D., 4.70 +/- 0.38 mmol/l) but in chemical and insulin-dependent diabetics there was a marked increase in both the mean diurnal glucose value and in the variability of the plasma glucose levels observed through the day (mean +/- S.D., 5.61 +/- 5.61 +/- 1.03 and 6.02 +/- 1.26 mmol/l respectively, P less than 0.01). No difference was observed between the peripheral insulin activity of the normal and chemical diabetic women, and the impaired glucose tolerance of the latter group was due to a deficient insulin response to goucose. The diurnal glucose variability, expressed as the standard deviation of the mean, was found to be inversely correlated with the residual C-peptide response in insulin-requiring diabetics. The mean diurnal plasma free fatty acid (FFA) concentration was slightly raised in chemical diabetic subjects compared to normal women (mean +/- S.D., 0.77 +/- 0.34 and 0.68 +/- 0.20 mmol/l respectively) but this difference was not significant. Insulin treatment produced a marked reduction in circulating FFA concentration, with a mean value in the insulin-dependent diabetic group of 0.45 +/- 0.11 mmol/l (P less than 0.001). Neonatal glucose assimilation during the first two hours of life correlated strongly with several functions of maternal carbohydrate tolerance. This was associated with higher plasma insulin concentrations at birth, and a marked tendency to hypoglycaemia in the infants of untreated chemical diabetic women. Impaired mobilization of triglyceride stores was also observed during the two hours after birth in the infants of diabetic women. This, however, appears to be due not to impaired lipolysis but to rapid re-esterification of FFA. These findings all indicate a state of functional hyperinsulinism in the infant of the diabetic women secondary to maternal hyperglycaemia.