Achieving the HbA1c Target Requires Longer Time in Range in
Continuous glucose monitoring (CGM) overcomes the limitations of glycated hemoglobin (HbA1c). This study was to investigate the relationship between CGM metrics and laboratory HbA1c in pregnant women with type 1 diabetes.

An observational study enrolled pregnant women with type 1 diabetes who wore CGM devices during pregnancy and postpartum from 11 hospitals in China. CGM data were collected to calculate time-in-range (TIR), time above range (TAR), time below range (TBR), and glycemic variability parameters. Relationships between the CGM metrics and HbA1c were explored. Linear and curvilinear regressions were conducted to investigate the best-fitting model to clarify the influence of HbA1c on the TIR-HbA1c relationship during pregnancy.

-- A total of 272 CGM data and corresponding HbA1c from 98 pregnant women with type 1 diabetes and their clinical characteristics were analyzed in this study.

-- Mean HbA1c and TIR were 6.49±1.29% and 76.16±17.97% during pregnancy, respectively.

-- HbA1c was moderately correlated with TIR 3.5-7.8, mean glucose and TAR 7.8, but was weakly correlated with TBR 3.5 during pregnancy.

-- On average, a 1% (11 mmol/mol) decrease in HbA1c corresponded to an 8.5% increase in TIR 3.5-7.8.

-- During pregnancy, HbA1c of 6.0%, 6.5% and 7.0% were equivalent to a TIR 3.5-7.8 of 78%, 74%, and 69%, respectively.

Conclusively, it was found that there was a moderate correlation between HbA1c and TIR 3.5-7.8 during pregnancy. To achieve the HbA1c target less than 6.0%, pregnant women with type 1 diabetes should strive for TIR 3.5-7.8 more than 78% (18h 43min) during pregnancy.