[Screening for gestational diabetes mellitus based on blood glucose 2hrs value after a 75g oral glucose load]

We examined the relationship between the time of blood collection and the blood glucose value by analyzing blood glucose values around one hour and two hours after a 75g oral glucose load in 50 women who were at 24 to 28 weeks of gestation. We performed a 75g, 2hrs screening test at 16 to 33 weeks of gestation on all 2,570 pregnant women who visited our out patient clinic between May, 1986 and August, 1991. 1. During the 50-70 minutes after glucose loading, the blood glucose level changed 15-20mg/dl every 10 minutes. During the 110-130 minutes after glucose loading, the change was smaller (10-15mg/dl). These results suggest that the blood glucose level is more stable at 120 minutes than at 60 minutes. 2. When the cut-off point was set at 130mg/dl, the screening test for GDM with a 75g, 2hrs value had a sensitivity of 100%, and a specificity of 85.5% and the incidence of GDM was 3.1%. A 75g, 2hrs screening test therefore seems to be as useful in detecting GDM as a 50g, 1-hour test and to be more suited to crowded out patient clinics because its ability to detect GDM is not seriously affected by small variations in the blood sampling time.