Lack of Validity of the Glucose Management Indicator in Type 1 Diabetes in Pregnancy

OBJECTIVE The glucose management indicator (GMI) is widely used as a replacement for HbA1c, but information in pregnancy is very limited. We assessed the accuracy of GMI and associations with pregnancy outcomes in type 1 diabetes.

RESEARCH DESIGN AND METHODS We compared HbA1c, continuous glucose monitoring (CGM) metrics, GMI at 12, 24, and 34 weeks’ gestation and outcomes in 220 women from the Continuous Glucose Monitoring in Women With Type 1 Diabetes in Pregnancy Trial (CONCEPTT) using logistic/linear regression and Bland-Altman plots.

RESULTS GMI equations performed less accurately in pregnancy, with higher bias, especially in first and third trimesters. GMI and mean CGM glucose had equivalent predictive capability over pregnancy outcomes. GMI did not offer additional predictive capability over time in range (63–140 mg/dL; 3.5–7.8 mmol/L), time above range (>140 mg/dL; >7.8 mmol/L), and average CGM glucose concentrations.

CONCLUSIONS GMI is not an accurate replacement for HbA1c in pregnancy in women with type 1 diabetes.