Selective screening for gestational diabetes mellitus. Toronto Trihospital Gestational Diabetes Project Investigators

The usual approach to detecting gestational diabetes mellitus is to screen all pregnant women by measuring their plasma glucose after a 50-g oral glucose load at 24 to 28 weeks' gestation. Women are referred for an oral glucose-tolerance test if the plasma glucose concentration one hour later is > or = 140 mg per deciliter (7.8 mmol per liter). We hypothesized that the efficiency of screening could be enhanced by considering women's risks of gestational diabetes on the basis of their clinical characteristics.

We studied 3131 pregnant women who underwent both the screening and the diagnostic tests. We randomly selected data on half the women and used them to derive new screening strategies. We categorized each woman's risk of gestational diabetes mellitus on the basis of her age, body-mass index before pregnancy, and race. We developed strategies that entailed no screening for low-risk women, usual care for intermediate-risk women, and universal screening with lower thresholds -- plasma glucose values of 130 mg per deciliter (7.2 mmol per liter) or 128 mg per deciliter (7.1 mmol per liter) -- for high-risk women. The strategies were validated with data on the other half of the women.

The new strategies allowed a 34.6 percent reduction in the number of screening tests performed (95 percent confidence interval, 32.3 to 37.0) and detected 81.2 to 82.6 percent of the women with gestational diabetes as compared with the 78.3 percent detected through usual care. The percentage of false positive screening tests was significantly reduced, from 17.9 percent with usual care to 16.0 per cent (P=0.02) or 15.4 percent (P<0.001) with the new strategies, depending on the threshold values for high-risk women.

Consideration of women's clinical characteristics allows efficient selective screening for gestational diabetes.