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In the United States, screening for gestational diabetes generally has been performed using a two-step approach: an initial 50-gram glucose challenge test, which is followed by a 100-gram oral glucose tolerance test for those who have an initial abnormal screen. This approach was recently investigated in a randomized clinical trial in the United States, and the results suggest that screening and treating those diagnosed with gestational diabetes reduces the risk of some perinatal complications, including macrosomia and shoulder dystocia.

Recently, another group of investigators tested a one-step screening and diagnostic strategy in which patients were screened and diagnosed based on a one-time, two-hour, 75-gram glucose tolerance test. The main advantage of this strategy is that it requires a single test, which likely would increase patient satisfaction and would be less expensive in the short-term than the two-step approach. In December 2010, the American Diabetes Association (ADA) recommended that providers in the United States use the one-step test. This recommendation has led to confusion and controversy among providers of obstetrical care.

The Committee on Obstetric Practice of the American College of Obstetricians and Gynecologists (ACOG) issued an opinion in August 2011 about the best strategy for gestational diabetes screening. Simply put, ACOG recommends that at this time the two-step process should remain the standard in the United States.

Screening and Diagnosis of Gestational Diabetes

The reasons for this are two-fold. First, due to false positives, the one-step, 75- gram test would lead to diagnoses of gestational diabetes in approximately 18 percent of subjects, compared to roughly 5 percent when using the two-step test. This high rate of “diagnosis” could lead to many unnecessary tests and interventions. Second, the one-step strategy has not been as well tested as the two-step strategy. For both of these reasons, according to ACOG, practitioners should use the two-step approach for screening and diagnosis of gestational diabetes.

We can expect to receive additional information on this issue soon. The Agency for Healthcare Quality and Research is developing an evidence-based document on screening for gestational diabetes. In addition, the National Institutes of Health (NIH) will hold a Consensus Conference on this issue in October 2012.

Additional Resources

  • Learn more about ACOG’s position on gestational diabetes testing at acog.org.
  • Visit the American Diabetes Association website to learn more about its recommendation of one-step screening at diabetes.org.
  • For additional information about the NIH Consensus Conference visit, consensus.nih.gov.
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