The effect of minor degrees of glucose intolerance on the incidence of neonatal macrosomia.

The incidence of neonatal macrosomia in infants of mothers who have only one abnormal value in a 3-hour glucose tolerance test (GTT) is greater than normal. Often, corrections for gestational age have not been used in the analysis, and in the few studies in which corrections were made, the results conflicted. In this study, the birth weights of infants from 157 patients who had only one abnormal GTT value were compared with the birth weights of infants from normal mothers, with and without correction for gestational age. Analysis using three different GTT criteria revealed that the incidence of birth weight greater than 4000 g was 20% or greater in the infants of mothers who had only one abnormal GTT value and only 12.4% in controls. However, when adjusted for gestational age, there were no differences in the birth weights and percentage of large for gestational age (LGA) infants in the study groups versus controls. The mean and gestational age-adjusted birth weights of the greater-than-4000-g neonates born to women with one abnormal GTT value were no different than those of controls. However, at delivery, the gestational ages of patients with one abnormal GTT value tended to be slightly greater than those of controls by 0.1-0.6 weeks, suggesting that minor degrees of abnormal glucose metabolism may prolong pregnancy in some patients. When compared with the literature, the findings of this study suggest that the National Diabetes Data Group criteria may be too high as a screen for LGA infants.