Glucose tolerance test: degree of glucose abnormality correlates with neonatal outcome

To determine how well the extent of glucose abnormality, as reflected by the number of abnormal values on the 3-hour oral glucose tolerance test (GTT), correlates with the level of carbohydrate intolerance during pregnancy and with the severity of adverse outcome.

We followed 764 gestational diabetic women under a once-per-week fasting and 2-hour postprandial serum glucose monitoring system. The subjects were stratified by the number of abnormal values on their GTTs. The level of glucose control and incidence of large for gestational age (LGA) infants were then determined and compared with the findings in 636 gravidas with abnormal screening but all normal GTT values.

Patients with one or more abnormal GTT values had comparable incidences of LGA infants, which were all significantly greater than that in the 0-abnormal group (23-27% versus 13%; P < .01). This difference was due to subjects with poor glucose control. The means of the GTT values for each sampling time were greater and the GTT periodicity (the time for the GTT curve to return to the fasting level) was longer with an increasing number of GTT abnormal values (zero versus one versus two versus three versus four abnormal values, P < .02). The mean fasting, 2-hour postprandial, and overall mean glucose values during the study were positively associated with the number of abnormal GTT values.

One or more abnormal GTT values were associated with comparably elevated incidences of LGA infants in patients with poor glycemic control. Achievement of recommended glucose control decreased adverse outcomes to near normal levels.