A Comparison of the 3 H Glucose Tolerance Test and the 2 H Value in Identifying Risk for Excessive Fetal Growth

Abstract

The objective of this study was to determine if the 2 h value of the glucose tolerance test (GTT) is as reliable as the complete GTT in identifying risk for excessive fetal growth. Five hundred eighty-eight patients underwent a 3 h oral GTT at 26–28 weeks' gestation. The 2 h value of the test was compared to the results of the GTT. The incidence of large for gestational age (LGA) infants was compared for patients who had an abnormal GTT or an abnormal 2 h value only. A normal 2 h value was associated with a normal GTT in 98.5% of cases, while an abnormal 2 h value was associated with an abnormal GTT in 70% of cases. An abnormal GTT was associated with a 22% incidence of LGA, while a 2 h value ≥165 mgm/dl was associated with a 20% incidence of LGA. This difference was not statistically significant. A single 2 h value GTT is more cost-effective and as predictive as a complete 3 h GTT in identifying risk for excessive fetal growth.