Do the new threshold levels for the diagnosis of gestational diabetes mellitus correctly identify women at risk?

Pregnant women with gestational diabetes mellitus (GDM) are at risk for certain neonatal complications. The International Association of the Diabetes and Pregnancy Study Groups (IADPSG) blood glucose level (BGL) diagnostic thresholds correspond to an odds ratio of at least 1.75 for selected complications (1). In the Hyperglycemia and Adverse Pregnancy Outcome (HAPO) study (2), 16.1% of subjects had GDM, with the majority (11.1%) having one elevated BGL only (1). As the thresholds are statistically validated, subjects with GDM must have a risk of $1.75. But is this the case? All three BGL thresholds were defined independently. For example, when the 2-h BGL threshold was defined, the impact of fasting and 1-h BGLs were not considered. Their elevation should increase the risk of complications associated with raised 2-h BGLs. Alternatively, could normal fasting and 1-h BGLs reduce that risk? Are two normal BGLs protective?