When there is a 3-fold difference in the number of patients being diagnosed with a disease depending on the diagnostic criteria applied, it’s certain to raise some eyebrows. This is the case for gestational diabetes mellitus (GDM). The prevalence of GDM can range from 7% to >20% depending on the diagnostic criteria used. A form of diabetes glucose intolerance that occurs during pregnancy and resolves upon termination of pregnancy, GDM can have profound consequences on both the developing fetus and the mother. This makes timely recognition and treatment essential. However, the diagnosis of diabetes in pregnancy is not as straightforward as one might expect.

In this morning’s session “Predicating and Diagnosing GDM: Are We Making Progress,” Florence Brown, MD, an endocrinologist, and Amy Valent, MD, an obstetrician, will present evidence for and against the two widely used screening methods for GDM diagnosis. Currently, diagnostic criteria vary between endocrine and obstetric organizations even within the same country.

Moderator David Sacks, MD, will set the stage, and note that societies are constantly changing their recommendations. The reason for the disagreement? There is simply too much to agree on: fasting versus random glucose or oral glucose tolerance tests (OGTTs), the diagnostic cutpoints, and whether one or multiple abnormal results are necessary for diagnosis.

The 2-step method for screening GDM is the oldest and most commonly used in the U.S. and recommended by the American College of Obstetricians and Gynecologists. With this approach, a 50-gram glucose load is administered as a screening test to determine whether a second 100-gram challenge is necessary for diagnosis. Proponents argue that it is the most cost-effective method for screening. However, most people will agree that the oral glucose load is an unpleasant experience—even intolerable during pregnancy.

In 2010 the International Association of Diabetes and Pregnancy Study Groups developed criteria using a 1-step approach, derived from the Hyperglycemia and Adverse pregnancy Outcome study. This approach is endorsed both by the American Diabetes Association and the Endocrine Society. Importantly, it is based on prevention of adverse pregnancy outcomes.

However, this method is not yet widely adopted. The argument against the use of this method is that diagnosis is based on a single glucose value above the cutoff which can lead to an increased number of false positives, and the benefits of using this criterion are not yet proven.

Both approaches detect GDM in 24-28 weeks of pregnancy, typically in the third trimester. There has been much interest in detecting and predicting onset of GDM earlier. Sacks will present evidence on whether detecting GMD earlier in pregnancy can be beneficial. He will also discuss alternative approaches for earlier detection going beyond the traditional markers of glycemia such as glucose and glycated proteins.

So which is the best method to diagnose GDM? And will the debate end any time soon on whether we can accurately predict GDM earlier in pregnancy? You’ll have to attend the session to find out.