The different screening and diagnostic methods for gestational diabetes mellitus (GDM) currently in clinical use have led the National Institutes of Health Office of Disease Prevention to organize a consensus conference to better understand the potential ramifications of changing the current screening and diagnostic criteria in the United States vs keeping current practices in place. Research has demonstrated that even mild forms of hyperglycemia potentially pose significant adverse health consequences for pregnant women and their children. Thus, it is anticipated that lowering the diagnostic criteria for GDM will significantly reduce morbidity and health care costs in the long term. However, such a change would dramatically increase the number of women identified as having this disease and place a significantly greater burden on an already overburdened primary health care system. Although several cost-benefit analyses suggest that such a change will improve health outcomes for mothers and babies, at least 1 study found that these anticipated public health benefits will not occur unless a higher level of care is devoted to these newly diagnosed patients. There also is a distinct possibility that changing the diagnostic criteria for GDM will increase cesarean delivery rates, which might offset many of the public health gains engendered by diagnosing more women with this condition. The scientific dilemma to change or not to change, thus, requires a rigorous analysis of the scientific, economic, practice, and legal pros and cons to achieve a satisfactory answer.