Continuous Glucose Monitoring (CGM) Profiles in Pregnancies with and without Gestational Diabetes Mellitus

Objective: To determine if continuous glucose monitor (CGM)-derived glycemic patterns can characterize pregnancies with GDM as diagnosed by standard oral glucose tolerance test at 24-28 weeks’ gestation compared to those without GDM. Research Design and Methods: The analysis includes 768 individuals enrolled from two sites prior to 17 weeks’ gestation between June 2020 and December 2021 in a prospective observational study. Participants wore blinded Dexcom G6 CGM throughout gestation. Main outcome of interest was a diagnosis of GDM by oral glucose tolerance test (OGTT). Glycemic levels in participants with GDM vs. without GDM were characterized using CGM-measured glycemic metrics. Results: Participants with GDM (n=58 [8%]) had higher mean glucose (109±13 vs. 100±8 mg/dL [6.0±0.7 vs. 5.6±0.4mmol/L], p<0.001), greater glucose standard deviation (23±4 vs. 19±3 mg/dL [1.3±0.2 vs. 1.1±0.2mmol/L], p<0.001), less time in range 63-120 mg/dL (3.5-6.7mmol/L) (70% ± 17% vs. 84% ± 8%, p<0.001), greater % time >120 mg/dL (>6.7mmol/L) (median 23% vs. 12%, p<0.001), and greater % time >140 mg/dL (>7.8mmol/L) (median 7.4% vs. 2.7%, p<0.001) than those without GDM throughout gestation prior to OGTT. Median percent time >120 mg/dL (>6.7mmol/L) and time >140 mg/dL (>7.8mmol/L) were higher as early as 13-14 weeks’ gestation (32% vs. 14%, p<0.001, and 5.2% vs. 2.0%, p<0.001, respectively) and persisted during the entire study period prior to OGTT. Conclusions: Prior to OGTT at 24-34 weeks’ gestation, pregnant individuals who develop GDM have higher CGM-measured glucose levels and more hyperglycemia compared to those who do not develop GDM.