Objective:To investigate the value and clinical significance of fasting plasma glucose (FPG) in early pregnancy (8-12 gestational weeks) as a predictor of gestational diabetes mellitus (GDM) among women with different pre-pregnancy body mass index (pre-BMI) categories.Methods:A retrospective study was conducted including 9 710 singleton pregnant women (FPG levels in early pregnancy ≤5.6 mmol/L) who underwent prenatal screening and delivery in Yuyao People's Hospital from January 2020 to December 2022. Participants were stratified based on their pre-BMI as follows: <18.5 ( n=1 406), ≥18.5 to <25.0 ( n=7 162), ≥25.0 to <30.0 ( n=978), and ≥30.0 kg/m 2 ( n=164). Within each pre-BMI category, women were further divided into four groups based on FPG levels in early pregnancy (<4.5, ≥4.5 to <4.8, ≥4.8 to <5.1, and ≥5.1 mmol/L). Univariate and multivariate logistic regression analysis were used to identify risk factors for GDM, and receiver operating characteristic (ROC) curve was applied to evaluate the efficacy of FPG in early pregnancy based on different pre-BMI in predicting GDM. Results:The overall incidence of GDM in the singleton pregnancy women with FPG levels in early pregnancy ≤5.6 mmol/L was 12.3% (1 197/9 710). For a pre-BMI of <18.5 kg/m 2, the ORs with 95% CIs for GDM within the different FPG categories (<4.5, ≥4.5 to <4.8, ≥4.8 to <5.1, and ≥5.1 mmol/L) were 0.041 (95% CI: 0.015-0.409), 1.834 (95% CI: 1.089-3.088), 6.779 (95% CI: 4.041-11.371), and 13.723 (95% CI: 5.560-33.871), respectively. For pre-BMI of ≥18.5 to <25.0 kg/m 2, the respective the ORs with 95% CIs were 0.048 (95% CI: 0.012-0.203), 2.573 (95% CI: 2.091-3.168), 9.023 (95% CI: 7.240-11.245), and 9.158 (95% CI: 6.484-12.937). For pre-BMI of ≥25.0 to <30.0 kg/m 2, the ORs with 95% CIs were 0.108 (95% CI: 0.053-0.446), 1.698 (95% CI: 1.064-2.654), 7.537 (95% CI: 5.285-13.080), and 9.994 (95% CI: 5.613-18.218). For pre-BMI of ≥30.0 kg/m 2, the ORs with 95% CIs were 0.098 (95% CI: 0.072-1.015), 2.888 (95% CI: 0.911-9.157), 13.674 (95% CI: 3.480-53.736), and 20.509 (95% CI: 6.674-63.019). The optimal cutoff value of FPG in early pregnancy for GDM prediction was 4.7 mmol/L with an area under the curve of 0.752, the risk of GDM significantly increased with FPG levels ≥4.7 mmol/L in early pregnancy across all pregnant women ( OR=17.356, 95% CI: 13.757-21.896, P<0.001). Conclusions:In the singleton pregnancy women with FPG levels in early pregnancy ≤5.6 mmol/L, FPG in early pregnancy is an independent risk factor for the occurrence of GDM; for pregnant women stratified by the same pre-BMI, the risk of developing GDM increases progressively with the rise of FPG in early pregnancy. FPG in early pregnancy has a certain value in predicting the occurrence of GDM.