Association of Continuous Glucose Monitoring Metrics with Pregnancy Outcomes in Patients with Pre-existing Diabetes

Objectives: Continuous glucose monitoring (CGM) improves maternal glycemic control and neonatal outcomes in type 1 diabetes pregnancies, compared to self-monitoring of blood glucose. However, CGM targets for pregnancy are based on expert opinion. We aimed to evaluate the association between CGM metrics and perinatal outcomes and identify evidence-based targets to reduce morbidity.

Research Design and Methods: Retrospective cohort study of pregnant patients with type 1 or 2 diabetes who used real-time CGM and delivered at a US tertiary center (2018-2021). Multiple gestations, fetal anomalies and early pregnancy loss were excluded. Exposures included time in range (TIR; 65-140mg/dL), time above range (TAR), time below range (TBR), glucose variability, average glucose, and glucose management indicator. The primary outcome was a composite of fetal or neonatal mortality, large- or small-for-gestational-age at birth, neonatal intensive care unit admission, hypoglycemia, shoulder dystocia or birth trauma, and hyperbilirubinemia. Logistic regression estimated the association between CGM metrics and outcomes, and optimal TIR was calculated.

Results: Of 117 patients, 16 (13.7%) used CGM before pregnancy and 68 (58.1%) had type 1 diabetes. Overall, 98 (83.8%) patients developed the composite neonatal outcome. All CGM metrics except TBR were associated with neonatal morbidity. For each 5%-point increase in TIR there was 28% reduced odds of neonatal morbidity (OR 0.72, 95% CI 0.58-0.89). The statistically optimal TIR was 66-71%.

Conclusions: Nearly all CGM metrics were associated with adverse neonatal morbidity and mortality and may aid management of pre-existing diabetes in pregnancy. Our findings support the ADA recommendation of 70% TIR.