Gestational diabetes mellitus (GDM) is a serious health condition that occurs in 4% to 12% of pregnancies, but recent research showing significant screening gaps for the disease makes the problem an even greater concern. At the same time, newly issued American Diabetes Association (ADA) guidelines for the diagnosis of GDM provide for streamlined laboratory testing, which may promote improved screening rates and health outcomes (Diabetes Care. 2011;34[Suppl 1]:S11-S61).
I recently coauthored a study that detailed the existing gaps in diabetes screening in pregnancy and postpartum, based on an analysis of de-identified test results of nearly one million pregnant
American women (Obstet Gynecol. 2011;117:61-88). The study underscores the need for the new ADA guidelines, issued in January 2011: The analysis showed that only two in three pregnant women aged 25 to 40 years (the age group at high risk for GDM, according to the previous ADA guidelines) were screened for the condition. And only one in five women diagnosed with GDM during pregnancy underwent postpartum testing.
The study further demonstrated significant differences in testing rates for GDM based on age, weight, and ethnicity. For instance, Asian women were nearly three times more likely to have GDM than Caucasian women. Asian women were also the ethnic group most likely to be screened. Obese women were more likely to have GDM but much less likely to be screened than low-weight women.
The ADA’s modified screening recommendations for GDM outline a new testing protocol, and could result in improved detection and, therefore, treatment. The guidelines are based on recommendations by the International Association of Diabetes and Pregnancy Study Groups (IADPSG) (Diabetes Care. 2010;33:676-682). The process of diagnosing GDM will follow new protocols, including testing high-risk women at their first neonatal appointment.
Additionally, all women without a prior diagnosis of diabetes (type I or type II) should receive a 75-g oral glucose tolerance test (OGTT) at 24 to 28 weeks’ gestation, regardless of age, ethnicity, or other factors. This recommendation represents a significant change in the ADA guidelines, which suggested using a 100-g OGTT, performed after a positive 50-g OGTT screen, to diagnose GDM. The former protocol required testing some women in two separate visits before a diagnosis could be made.
Under the ADA guidelines, testing should occur after an overnight fast of at least eight hours. And, a diagnosis should be made when any one glucose concentration exceeds the values identified for three specimens taken at fasting (baseline level of 92 mg/dL), one hour (180mg/dL), and two hours (153 mg/dL).
The new ADA guidelines also address postpartum screening. An estimated 40% to 60% of women with gestational diabetes will develop type 2 diabetes within 10 years. The ADA recommends that women diagnosed with GDM be screened for postpartum-persistent diabetes at six to 12 weeks postpartum, with follow-up screening every three years. This may improve disease management for affected women.
While the research by my colleagues at Quest Diagnostics and me demonstrates that many women are not adequately screened for gestational or postpartum diabetes, I am optimistic that the new ADA guidelines will make it easier to diagnose these serious disorders. n