Controversy regarding the diagnosis and management of gestational diabetes mellitus (GDM) has continued for several decades. Until recently, there has been a lack of large robust prospective studies to drive evidence-based recommendations regarding the screening and diagnosis of GDM. The HAPO (Hyperglycemia and Adverse Pregnancy Outcome) study, which was published in 2008 in the New England Journal of Medicine, was undertaken to determine if maternal hyperglycemia less than in established gestational diabetes was associated with an increased risk for adverse pregnancy outcomes. Investigators from this study found that, in fact, the mean fasting and postprandial glucose concentrations associated with adverse outcomes were lower than the current criteria for diagnosis of gestational diabetes. They observed a strong, continuous association of maternal glucose levels with increased birth weight and increased cord blood serum C-peptide levels was observed. Although no obvious thresholds at which risks increased were discovered, they found that the lower the threshold, the greater the prevalence of GDM and the more women requiring treatment.
In March of 2010, based on the findings from HAPO and several other trials, the IADPSG (International Association of Diabetes and Pregnancy Study Groups) Consensus Panel recommended the use of the 2-h 75-g OGTT or one-step approach to diagnosis GDM. OGTT thresholds of 92 mg/dL fasting, 180 mg/dL at 1 h, and 153 mg/dL at 2 h were proposed. In 2011, these recommendations were adopted by the American Diabetes Association and published in their Clinical Practice Guidelines and Standards of Medical Care in Diabetes.
However in September of that same year, The American College of Obstetricians and Gynecologists published their Committee Opinion (# 504) continuing to recommend a two-step approach to the screening and diagnosis of GDM. The report stated that there was no evidence that diagnosis using the new criteria (now endorsed by both IADPSG and ADA) leads to clinically significant improvements in outcomes and would lead to a significant increase in health care costs.
Therefore, at the current time the controversy regarding the screening and diagnosis of GDM remains unresolved. The National Institutes of Health have convened a consensus development conference which will be held in October in Bethesda, Maryland to hopefully bring resolution to this issue.