Achieving the HbA(1c) Target Requires Longer Time in Range in Pregnant Women With Type 1 Diabetes

CONTEXT: Continuous glucose monitoring (CGM) overcomes the limitations of glycated hemoglobin (HbA(1c)). OBJECTIVE: This study aimed to investigate the relationship between CGM metrics and laboratory HbA(1c) in pregnant women with type 1 diabetes. METHODS: An observational study enrolled pregnant women with type 1 diabetes who wore CGM devices during pregnancy and postpartum from 11 hospitals in China from January 2015 to June 2019. 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 HbA(1c) were explored. Linear and curvilinear regressions were conducted to investigate the best-fitting model to clarify the influence of HbA(1c) on the TIR-HbA(1c) relationship during pregnancy. RESULTS: A total of 272 CGM data and corresponding HbA(1c) from 98 pregnant women with type 1 diabetes and their clinical characteristics were analyzed in this study. Mean HbA(1c) and TIR were 6.49 ± 1.29% and 76.16 ± 17.97% during pregnancy, respectively. HbA(1c) was moderately correlated with TIR(3.5-7.8)(R = –0.429, P = .001), mean glucose (R = 0.405, P = .001) and TAR(7.8) (R = 0.435, P = .001), but was weakly correlated with TBR(3.5) (R = 0.034, P = .001) during pregnancy. On average, a 1% (11 mmol/mol) decrease in HbA(1c) corresponded to an 8.5% increase in TIR(3.5–7.8). During pregnancy, HbA(1c) of 6.0%, 6.5%, and 7.0% were equivalent to a TIR(3.5–7.8) of 78%, 74%, and 69%, respectively. CONCLUSION: We found there was a moderate correlation between HbA(1c) and TIR(3.5–7.8) during pregnancy. To achieve the HbA(1c) target of less than 6.0%, pregnant women with type 1 diabetes should strive for a TIR(3.5–7.8) of greater than 78% (18 hours 43 minutes) during pregnancy.