Evaluation of the three-hour oral glucose tolerance test in detection of significant hyperglycemia and hypoglycemia in pregnancy.

Analysis of 2,000 consecutive patients who had a three-hour 50-gm. oral glucose tolerance test done in the third trimester of pregnancy has shown that the three-hour reading was not necessary for the diagnosis of gestational diabetes. It was found that hyperglycemia and hypoglycemia (95th and 5th percentiles, respectively, for plasma glucose levels) were significantly associated with an increased risk for perinatal mortality. Furthermore, hyperglycemia was associated with an increased incidence of large-for-dates placentas and hypoglycemia with small-for-dates infants and small-for-dates placentas. These associations with hypoglycemia were seen to be greatest when this occurred at the three-hour level, and it was concluded that the three-hour measurement should be retained until the clinical significance of hypoglycemia in pregnancy is fully determined.