Qianruo Pan, Zhuhua Cai, Dongmei Lin, Liqiong Chen, Junmiao Xiang
INTRODUCTION: Gestational diabetes mellitus (GDM) is closely related to insulin resistance (IR) and is usually diagnosed in mid-pregnancy, limiting opportunities for early risk identification. We evaluated six simple first-trimester IR indices—triglyceride-glucose index (TyG), triglyceride-glucose–body mass index (TyG-BMI), triglyceride/high-density lipoprotein cholesterol ratio (TG/HDL-C), metabolic score for insulin resistance (METS-IR), Zhejiang University index (ZJU), and hepatic steatosis index (HSI)—for predicting GDM and oral glucose tolerance test (OGTT) glucose levels. METHODS: In this retrospective study of 2122 Chinese pregnant women, GDM was diagnosed using a 75-g OGTT at 24–28 weeks. Fasting blood samples in early pregnancy were used to calculate IR indices. Logistic regression assessed associations with GDM and OGTT results; ROC analyses evaluated predictive performance. RESULTS: All indices were positively associated with GDM and OGTT measures, except HSI, which correlated with fasting and 1-hour glucose only. TyG-BMI showed the best discrimination for GDM (AUC 0.65; 95% CI 0.617–0.683), and METS-IR performed best for fasting glucose (AUC 0.736). Indices generally predicted fasting glucose more accurately than postprandial glucose or overall GDM. Associations were linear and consistent across subgroups. CONCLUSIONS: First-trimester TyG, TyG-BMI, TG/HDL-C, METS-IR, ZJU, and HSI are independent predictors of GDM and correlate with OGTT glucose, particularly fasting glucose.