(172) Continuous glucose monitoring in type 2 and gestational diabetes in pregnancy: better than hemoglobin A1c?

In gravidas with type 2 diabetes (T2DM) and gestational diabetes (GDM), we sought to determine the ability of continuous glucose monitoring (CGM) metrics (time-in-range, TIR; time-above-range, TAR; time-below-range, TBR; glycemic variability, GV) and hemoglobin A1c (HbA1c) to distinguish those at risk of adverse perinatal outcomes (APOs).

Study Design:

In a retrospective study (2019-22) of gravidas with T2DM/GDM who used CGM with target range 70-140 mg/dl, we assessed average 3^rd trimester TIR, TAR, TBR, GV, and HbA1c in those with (vs. without) the following APOs: hypertensive disorders of pregnancy (HDP), large-for-gestational age neonate (LGA, birthweight ≥ 90%ile), neonatal intensive care unit (NICU) admission, neonatal hypoglycemia (NH, glucose ≤ 40 within 24 hours of birth), and jaundice (requiring phototherapy). For each outcome, the Mann-Whitney U test compared median CGM metrics and HbA1c, and receiver operating characteristic (ROC) analysis determined the optimal cut-point and area under the curve (AUC) for each metric.

Results:

Of 48 and 22 eligible gravidas with T2DM and GDM, respectively, lower TIR (p ≤ 0.03) and higher TAR (p ≤ 0.04) was associated with both HDP and NICU admission. HbA1c was higher in gravidas who had LGA infants and NICU admission (p ≤ 0.02), and discriminatory ability of HbA1c exceeded that of all CGM metrics assessed (AUC for HbA1c: LGA 0.75, NICU 0.71). However, for HDP, a difference in HbA1c was not observed (p=0.26) and HbA1c had poor discriminatory ability (AUC 0.61). Neither HbA1c nor any of the CGM metrics differed among those with (vs. without) neonatal hypoglycemia or jaundice, and discriminatory ability of all metrics for these outcomes was poor (AUC ≤ 0.7).

Conclusion:

In this cohort, HbA1c had superior discriminatory ability than CGM metrics for LGA and NICU admission among pregnancies affected by T2DM/GDM, but further investigation is warranted to identify the optimal measure of glycemic control that can prognosticate risk of other APOs in this population.