Reassessment of the new diagnostic thresholds for gestational diabetes mellitus: an opportunity for improvement.

The International Association of Diabetes and Pregnancy Study Groups has recommended new blood glucose levels (BGLs) for the diagnosis of gestational diabetes mellitus (GDM). These BGLs supposedly identify women with at least a 75% increased risk of developing certain adverse neonatal outcomes. The new criteria result in a significant increase in the number of women diagnosed with GDM. Most of the women diagnosed with GDM according to the new criteria have only one elevated BGL. Due to the unrecognised effect of the other BGLs being normal, up to 50% of these women are inappropriately diagnosed with GDM as they do not meet the agreed risk threshold. In absolute terms, for every 100 women diagnosed with GDM who have only one elevated BGL, nearly 50 do not meet the agreed risk threshold for diagnosis, and there are only up to seven extra cases of large-for-gestational-age infants. A more statistically valid basis for diagnosing GDM consistent with the recommended risk threshold is suggested.