1,5-Anhydroglucitol as a marker of maternal glycaemic control and predictor of neonatal birthweight in pregnancies complicated by type 1 diabetes mellitus

AIMS/HYPOTHESIS: Most pregnant women with type 1 diabetes mellitus achieve HbA(1c) targets; however, macrosomia remains prevalent and better pregnancy glycaemic markers are therefore needed. 1,5-Anhydroglucitol (1,5-AG) is a short-term marker of glycaemia, reflecting a period of 1 to 2 weeks. Its excretion rate depends on the renal glucose threshold and thus it is unclear whether it may be used in pregnant type 1 diabetes women. We evaluated 1,5-AG as a glycaemic marker and birthweight predictor in pregnant women with type 1 diabetes, and compared its performance with HbA(1c). METHODS: 1,5-AG and HbA(1c) were measured in 82 pregnant women with type 1 diabetes. In addition, 58 continuous glucose monitoring system (CGMS) records were available. Macrosomia was defined as birthweight >90th centile. The data were analysed with Pearson’s correlations, and linear and logistic regression models. Receiver operating characteristic (ROC) analysis was used to evaluate third trimester 1,5-AG as a predictor of macrosomia. RESULTS: Unlike HbA(1c), 1,5-AG strongly correlated with CGMS indices: the AUC above 7.8 mmol/l (r = −0.66; p < 0.001), average maximum glucose (r = −0.58; p < 0.001) and mean glucose (r = −0.54; p < 0.001). In the third trimester, 1,5-AG was the strongest predictor of macrosomia, with ROC AUC 0.81 (95% CI 0.70, 0.89). In contrast, HbA(1c) in the third trimester had a ROC AUC of 0.69 (95% CI 0.58, 0.81). The best discrimination was achieved when both markers were used jointly, yielding a ROC AUC of 0.84 (95% CI 0.76, 0.93). CONCLUSIONS/INTERPRETATION: In pregnant women with type 1 diabetes, 1,5-AG is a better glycaemic marker than HbA(1c), as assessed by CGMS. A decreased third trimester 1,5-AG level, either singly or with HbA(1c), is a strong predictor of macrosomia.