Performance of flash continuous glucose monitoring and glycemic marker correlations in Chinese pregnant women with non-type 1 diabetes.

Maternal diabetes significantly increases the risk of adverse maternal and neonatal outcomes. Traditional self-monitoring of blood glucose is often invasive and limited in its ability to capture glycemic variability. Flash continuous glucose monitoring (FCGM) offers a promising alternative; however, its reliability and correlation with biochemical markers such as hemoglobin A1c (HbA1c) and glycated albumin (GA) in pregnant women with gestational diabetes mellitus (GDM) and type 2 diabetes mellitus (T2DM) remain underexplored. To evaluate the performance of the FreeStyle Libre H FCGM against plasma glucose and its correlations with HbA1c and GA. This prospective observational study involved 152 pregnant women with GDM or T2DM, with intermittent collection of venous plasma glucose, HbA1c, GA, and concurrent FCGM data at regular intervals at a single center. Relationships were evaluated using restricted cubic spline and mixed-effects models. Receiver operating characteristic curve analysis was performed to compare the ability of HbA1c and GA to detect suboptimal glycemic control. Analysis of 507 FCGM-plasma glucose pairs revealed an overall mean absolute relative difference of 7.96%. Mean absolute relative differences were 9.22%, 7.75%, and 4.15% for low (3.5-4.4 mmol/L), medium (4.5-7.8 mmol/L), and high (7.9-13 mmol/L) glucose levels, respectively. Most values fell within zone A or zone B on the Clarke and Parkes Error Grids. Bland-Altman analysis indicated a slight underestimation by FCGM (-0.121 mmol/L). Restricted cubic spline analysis revealed significant linear or nonlinear associations between HbA1c/GA and mean glucose, time in range, time above range, and coefficient of variation, but not time below range. Both HbA1c and GA were influenced by gestational age and pregestational body mass index. Receiver operating characteristic analysis showed that HbA1c had comparable or superior performance to GA in detecting suboptimal glycemic control based on FCGM-derived thresholds. The FCGM system served as a validated reference for evaluating glycemic markers in pregnant women with T2DM and GDM. HbA1c reliably assessed average glycemia, while GA provided complementary insight.