Criteria for screening and diagnosis of gestational diabetes mellitus in the first trimester of pregnancy.

OBJECTIVE To propose new cutoffs in plasma glucose levels in screening and diagnosis of gestational diabetes mellitus (GDM) in the first trimester of pregnancy. METHODS A 50-gram oral glucose challenge test (GCT) was performed in 1,716 singleton pregnancies at 6-14 weeks' gestation. In those with a positive GCT, a 100-gram glucose tolerance test (GTT) was carried out. The GCT and as necessary the GTT were repeated at 20-30 weeks. The relation of the results of the GCT and GTT at 6-14 weeks to that at 20-30 weeks was examined. RESULTS The diagnosis of GDM was made in 85 cases. In the GCT, there was a significant association between 1-hour plasma glucose levels at 6-14 weeks and at 20-30 weeks (r = 0.558, p < 0.0001), and in all cases of GDM, the level was 130 mg/dl or more at 6-14 weeks and 140 mg/dl or more at 20-30 weeks. In the GTT, the plasma glucose 1, 2 and 3 h after the 100-gram glucose load at 6-14 weeks was, respectively, 18, 29 and 35% lower than at 20-30 weeks. CONCLUSION Effective diagnosis of GDM in the first trimester can be achieved by lowering the GCT and GTT plasma glucose cutoffs.