Screening and diagnosis of gestational diabetes

A number of different recommendations have been made regarding screening and diagnostic testing for gestational diabetes. Although the ideal blinded study of the natural history of gestational diabetes has not been reported, nor has the perfect randomized clinical trial of various forms of treatment been performed, it seems likely that gestational diabetes has adverse effects on pregnancy outcome, and it is clear that this condition is a risk factor for subsequent diabetes. The problem remaining to be resolved is the precise level of glucose abnormality at which intervention may be beneficial. Once that is established, cost-benefit considerations can be applied to various screening recommendations. For the present, we have chosen to screen all pregnant women at 24 to 28 weeks gestation, using a 50-g, 1-hour oral glucose challenge. If the plasma glucose, determined in a standard laboratory analyzer using an enzymatic method, is greater than or equal to 130 mg/dL, a diagnostic 3-hour OGTT is recommended. Gestational diabetes is diagnosed based on thresholds outlined in Table 6. A survey by Landon and Gabbe in 1990 found that despite the ACOG recommendations, three fourths of generalist obstetricians and 90% of Maternal Fetal Medicine subspecialists report that they perform universal screening for gestational diabetes.