Continuous Glucose Monitoring Metrics and Pregnancy Outcomes in Women With Gestational Diabetes Mellitus: A Secondary Analysis of the DiGest Trial

Continuous glucose monitoring (CGM) is increasingly used in gestational diabetes mellitus (GDM), but optimal metrics, ranges, and targets in this population are undefined. We assessed associations between CGM metrics and pregnancy outcomes in GDM. During the DiGest study, 425 women with GDM (diagnosed at median IQR 25.1 18.3-27.7 weeks) and BMI ≥25 kg/m2 received a dietary intervention, with masked Dexcom G6 CGM at 29 (n = 361), 32 (n = 215), and 36 (n = 227) weeks' gestation. For this secondary analysis, we used logistic regression, receiver operating characteristic curves, and the Youden index to assess associations and predictive ability of CGM metrics, including pregnancy-specific time in range (TIRp) (63-140 mg/dL 3.5-7.8 mmol/L) and pregnancy outcomes. CGM metrics at 29 weeks were significantly associated with large for gestational age (LGA) and small for gestational age (SGA). Participants achieving mean glucose <110 mg/dL (6.1 mmol/L), TIRp ≥90%, or pregnancy-specific time above range (TARp) <10% at 29 weeks had a significantly lower risk of LGA (odds ratio OR 0.41 95% CI 0.22, 0.77, 0.38 0.20, 0.70, and 0.39 0.20, 0.73, respectively) and SGA (0.26 0.08, 0.79, 0.30 0.10, 0.91, and 0.19 0.06, 0.62, respectively). TARp <10% and mean nocturnal glucose <110 mg/dL (6.1 mmol/L) were associated with a reduced odds of preterm birth (OR 0.40 0.17, 0.94 and 0.42 0.19, 0.97, respectively). A stricter range (63-120 mg/dL 3.5-6.7 mmol/L) had similar performance overall, but had no single statistically robust TIR/TAR target across all outcomes. In women with GDM, CGM mean glucose <110 mg/dL (6.1 mmol/L), ≥90% TIRp, or <10% TARp using a range of 63-140 mg/dL (3.5-7.8 mmol/L) at 29 weeks' gestation was associated with a low risk of suboptimal offspring outcomes.