(DCP053) LOWERING THE DIAGNOSTIC THRESHOLD FOR GESTATIONAL DIABETES: A RETROSPECTIVE COHORT STUDY

Background: Gestational diabetes mellitus (GDM) is one of the most common complications of pregnancy and can lead to adverse outcomes for both mother and offspring. Studies indicate that sufficient maternal glycemic control decreases the risk of adverse outcomes. However, the optimal GDM diagnostic test or cut-points remains controversial. The Diabetes Canada 2018 guidelines suggest two approaches to screen for GDM; both include a fasting 75-gram oral glucose tolerance test (OGTT), but with different diagnostic cut-points. Our study focused on women with OGTT results between these two sets of thresholds, which we refer to as "grey zone" results.

METHODS AND RESULTS: This retrospective cohort study evaluated the association of higher versus lower cut-points in the second step of the OGTT with adverse maternal and neonatal outcomes. Specifically, we examined the risk of large for gestational age (LGA) and secondary outcomes in women with grey zone results who were not diagnosed with GDM compared to those who also had grey zone results but received a GDM diagnosis. Data were collected from pregnant women undergoing GDM screening tests between September 01, 2013, and February 29, 2020, at two Montreal-area university hospitals. Both hospitals follow the Diabetes Canada preferred two-step diagnostic approach. However, Centre A uses the Diabetes Canada thresholds with higher cut-points for the OGTT, whereas Centre B uses lower cut-points.
Of 4407 pregnancies evaluated, 840 met the inclusion criteria. Compared with women with grey zone results who received diagnosis and intervention for GDM, untreated women with grey zone results were less likely to have induction of labour (odds ratio (OR) 0.28, 95% CI 0.11, 0.68), and though inconclusive, had an increased OR point estimate for LGA (OR 1.90, 95% CI 0.77, 4.71).

Conclusion: Untreated pregnant women with mild hyperglycemia who were diagnosed with GDM by applying lower cut-points may benefit from intervention to reduce the risk of fetal overgrowth. However, our conclusions are limited by small sample size and institutional differences in clinical practice. Additional research is needed to determine if lower diagnostic thresholds can improve pregnancy outcomes.