Twenty women with abnormal glucose tolerance, detected from a routine program of antenatal screening for gestational diabetes mellitus (GDM) at 28 wk, were admitted for 24-h metabolic profiles. They were then alternately allocated to either insulin and dietary restriction or dietary restriction alone and then retested 4 wk later while on therapy. Ten normal controls were assessed twice at similar gestations to the study group. Before treatment, the 20 gestational diabetic subjects had higher mean concentrations of plasma glucose and 3-hydroxybutyrate than the controls for most of the profile, but mean insulin values were similar.

Insulin therapy was associated with a reduction in mean glucose concentrations so that the profile was similar to the controls, while in the diet-alone group the reduction was less. The 3-hydroxybutyrate concentrations rose between profiles in the normal group and also rose in those treated by diet alone, but still remained within the upper range of normal even at night. Insulin therapy resulted in a similar 3-hydroxybutyrate profile to the controls. The C-peptide response to breakfast was reduced in both groups to levels below that of the controls.

Neonatal outcome indices were similar in the two treatment groups, despite the differences in maternal metabolites, but because of the size of this study, conclusions about the neonate must be tentative.

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