Comparison of Glycemic Metrics Measured Simultaneously by Intermittently Scanned Continuous Glucose Monitoring and Real-Time Continuous Glucose Monitoring in Pregnant Women with Type 1 Diabetes

Background: We aimed to compare clinically important glycemic metrics with focus on mean sensor glucose and time-below-target range (TBR) during nighttime obtained with intermittently scanned continuous glucose monitoring (isCGM) and real-time CGM (rtCGM) in early pregnancy in women with type 1 diabetes. Materials and Methods: A prospective, observational study including 20 women with type 1 diabetes simultaneously monitored with isCGM (Freestyle Libre; Abbott) and rtCGM (Envision™ Pro; Medtronic) for 7 days in early pregnancy. Time-in-target range (TIR) was defined as 3.5-7.8 mmol/L. Results: Gestational age was median 66 (interquartile range 63-74) days and HbA1c was 48 mmol/mol (43-54). Median difference between isCGM and rtCGM was 0.1 mmol/L (-0.1 to 0.5) (P = 0.50) and -0.1 mmol/L (-0.4 to 0.2) (P = 0.35) for 24 h and during nighttime, respectively. For 24 h, TBR was 3.9% (1.6-7.0) versus 2.0% (0.6-3.7) (P = 0.06) and TIR was 57.2% (50.8-76.5) versus 69.6% (55.4-81.5) (P = 0.001) for isCGM and rtCGM, respectively. During nighttime TBR was 6.5% (0.4-16.7) versus 0% (0.0-0.8) (P = 0.003), TIR was 55.4 (41.1-81.0) versus 68.8 (52.4-80.3) (P = 0.005) and 75% versus 40% of the women had ≥1 glucose reading <3.5 mmol/L. Conclusions: In pregnant women with type 1 diabetes, mean sensor glucose was reported similar when measured by isCGM and rtCGM. However, during nighttime isCGM measured a clinically relevant higher percentage of TBR compared with rtCGM. Thus, the type of CGM device used may influence adjustments of insulin dose based on the concern for nocturnal hypoglycemia. ClinicalTrials.gov (NCT03770767).