The International Association of Diabetes in Pregnancy Study Group’s recommendations on diagnosis and classification of hyperglycemia in pregnancy give us, for the first time, the opportunity to put the diagnosis of gestational diabetes mellitus on a sound and evidence-based footing.

What are the advantages of the International Association of Diabetes in Pregnancy Study Group’s recommendations? First, they are based on a simplified diagnostic approach. Rather than the current 2-stage screening and diagnostic schema, pregnant women will undergo 1 test for gestational diabetes mellitus: a 75-g 2-hour oral glucose tolerance test. Second, the diagnostic thresholds are based explicitly on the relationship to pregnancy outcomes, whereas existing diagnostic thresholds were chosen, somewhat incredibly, solely for their ability to presage future overt diabetes mellitus. Moreover, the data from which the thresholds are derived (blinded investigations on >25,000 participants in the Hyperglycemia and Adverse Pregnancy Outcomes study) have been adjusted for multiple potential confounders that included geographic region, age, body mass index, parity, fetal gender, smoking and alcohol consumption, family history of diabetes mellitus, and gestational age at oral glucose tolerance test. That is, the data are robust and generalizeable. Third, the pregnancy outcomes that were chosen to inform the diagnostic thresholds are specific to the pathophysiologic condition of hyperglycemia in pregnancy: large for gestational age infant, fetal fat mass, and fetal hyperinsulinemia. Fourth, a rigid but pragmatic statistical framework was used to choose the thresholds. Fifth, randomized trial evidence from 2 well-done trials is now available to show that diagnosis and treatment of mild gestational diabetes mellitus, in fact, is associated with improved pregnancy outcomes.

The principal argument against adoption of the proposed guidelines is that they would markedly increase the proportion of pregnant women who are diagnosed with gestational diabetes mellitus, from the current level of approximately 5% to an anticipated level of 18%. Yes, this would be a “sea” change. However, most women who will be diagnosed by the proposed guidelines could be treated by diet alone, 80% and perhaps >90% based on the randomized trials. Although a rate of 18% should give us pause, it should not totally surprise us, because 29% of the United States adult population currently has diabetes mellitus or prediabetes mellitus. No doubt, implementation of the proposed guidelines would be challenging. But, if done right, these challenges will be rewarded with better maternal and infant health.