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Diagnosis of Gestational Diabetes Mellitus

An independent panel convened by the National Institutes of Health has concluded that despite potential advantages of adopting a new diagnostic approach for gestational diabetes mellitus (GDM), more evidence is needed to ensure that the benefits outweigh the harms. The panel recommended following the current diagnostic approach until further studies are conducted.

“The panel believes that cost-benefit, cost-effectiveness, and cost-utility research is needed to more fully understand the implications of changing diagnostic protocols for GDM,” said Dr. Peter VanDorsten, conference panel chairperson and Lawrence L. Hester, Jr. Professor, Medical University of South Carolina, Charleston.

GDM is a condition in which women without previously diagnosed diabetes exhibit high blood glucose levels during pregnancy. GDM is currently estimated to occur in 5-6 percent of U.S. pregnancies, affecting more than 240,000 births annually. GDM is associated with an increased risk of complications for both the mother and child, including maternal high blood pressure, cesarean delivery, and neonatal low blood sugar. In addition, up to half of women who have experienced GDM will develop type 2 diabetes later in life.

Different approaches are used to identify GDM, and the number of women diagnosed varies with the test criteria used. Tests differ based on whether there is a need for fasting, the grams of glucose given, the number of appointments, and the glucose threshold for diagnosis. Most health providers in the U. S. use a two-step approach that involves a nonfasting glucose screening of all pregnant women, followed by a glucose tolerance test for a subset. However, many other countries and prominent organizations, such as the American Diabetes Association, now support a one-step approach for all pregnant women. There is much debate regarding choice of tests and the trade-offs of each approach.

The panel identified certain operational advantages to the one-step approach, including a consistent diagnostic standard across the lifespan and better comparability of research outcomes globally. From a clinical perspective, the one-step approach could promote better standardization of patient care and allow a diagnosis to be achieved within the context of one visit as opposed to two.

However, despite potential benefits, there are several concerns about the one-step process. This approach is anticipated to increase the frequency of the diagnosis by two- to threefold, to a prevalence of approximately 15–20 percent. It is not known whether the additional women identified and their children will benefit from treatment. There is evidence that the labeling of these women may have unintended consequences, such as an increase in anxiety, clinic visits, cesarean delivery, and more intensive antenatal and newborn assessments. Moreover, the additional visits and testing to care for these women would impact their lives and would generate additional healthcare costs.

“The panel believes that there is not presently sufficient evidence to adopt a one-step approach. We are particularly concerned that the adoption of new criteria would increase the prevalence and the corresponding costs of GDM, without clear demonstration of improvements in key short- and long-term outcomes,” said Dr. VanDorsten. “However, given the potential benefits of a one-step approach, resolution of these concerns would change our conclusion.”

The panel suggested that additional research be conducted to resolve key research gaps. An initial step would be to assess cohorts that are using the single test approach to determine if more stringent diagnostic criteria would identify a population similar in prevalence and risk to that currently identified by the two-step approach now in use in the U. S. Subsequent research that focuses on women with less severe disease could help to determine if they would similarly benefit from this diagnostic approach.

Health services research should be performed to see if less expensive but equally or more effective approaches can be found for the management of GDM. The panel further recommended that prospective cohort studies of the real-world impact of GDM treatment on care utilization be conducted. It also supported additional research to understand patient preferences and the psychological consequences of a diagnosis, given that different approaches represent different burdens for patients.

The panel stated that studies should be conducted on interventions during pregnancy that can lead to long-term improvements in the health of women, children, and families. Healthy lifestyle interventions for women diagnosed with GDM, such as physical activity and medical nutrition therapy, may be of value.

“Pregnancy is the window into the future health of women, and the opportunity to make healthy changes during that critical time should not be missed,” said Dr. VanDorsten.

An updated version of the panel’s draft statement, which incorporates public comments received during the conference, can be viewed at

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