Lowering the Diagnostic Threshold for Gestational Diabetes: A Comparison of 2 Centres

In this study, we compared 2 gestational diabetes mellitus (GDM) diagnostic thresholds in relation to large-for-gestational-age (LGA) status and secondary adverse pregnancy outcomes.

This retrospective cohort study examined 840 pregnant women who underwent 2-step GDM screening at 2 hospital centres in Montréal that use distinct GDM diagnostic thresholds. At the second step of GDM screening, one centre used glucose thresholds suggested by the Diabetes Canada preferred approach and the other centre used the lower International Association of Diabetes and Pregnancy Study Groups thresholds. We defined mild hyperglycemia (MH) as having intermediate glucose values that were diagnostic of GDM at one centre but not the other (fasting plasma glucose [PG] 5.1 to 5.2 mmol/L, 1-hour PG 10 to 10.5 mmol/L, or 2-hour PG 8.5 to 8.9 mmol/L). We conducted multivariable linear and logistic regression analyses to evaluate outcomes for women with untreated or treated MH compared to those diagnosed with GDM by higher glucose thresholds within the same centre, and we also explored differences between centres.

The odds of LGA offspring were 3-fold higher (adjusted odds ratio [OR] 3.01, 95% confidence interval [CI] 1.47 to 6.19) among women with untreated MH compared with women treated for GDM at the same centre. Also, the odds of macrosomia were over 2-fold higher when comparing treated MH with GDM. In addition, untreated compared with treated MH had lower odds of induction of labour (adjusted OR 0.28, 95% CI 0.11 to 0.70).

Failure to optimally treat MH during pregnancy is associated with fetal overgrowth and may affect obstetrical management.