Predictive value of six first-trimester insulin resistance indices for gestational diabetes mellitus and oral glucose tolerance test results

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. 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. 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. 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.