Objective To investigate the predictive value of the triglyceride glucose-body mass index (TyG-BMI) and blood lipid levels on pregnancy outcomes in advanced-age pregnant women with gestational diabetes mellitus (GDM). Methods A retrospective study was conducted on 300 advanced-age GDM patients who underwent prenatal examination and delivery at our hospital from September 2023 to July 2024, designated as the GDM group. Additionally, 350 healthy advanced-age pregnant women who attended our hospital during the same period were selected as the control group. Based on pregnancy outcomes, the GDM group was further divided into an adverse outcome group (n=109) and a good outcome group (n=191). Basic data, pregnancy outcomes, TyG-BMI index, and blood lipid levels were compared between the GDM group and the control group. Univariate and multivariate analyses were performed to identify factors associated with adverse pregnancy outcomes in advanced-age GDM patients. The predictive value of each indicator was evaluated by drawing receiver operating characteristic (ROC) curves. Results The incidence of adverse pregnancy outcomes was significantly higher in the GDM group than in the control group. Compared to the control group, the GDM group had higher TyG-BMI index, TC, TG, and LDL-C levels, and lower HDL-C levels. Among advanced-age GDM patients, there were no statistically significant differences in age, gestational weeks, or primiparity between the adverse outcome group and the good outcome group. The adverse outcome group had significantly higher HbA1c, FPG, TyG-BMI index, TG, TC, and LDL-C levels, and significantly lower HDL-C levels than the good outcome group. Multivariate logistic regression analysis showed that HbA1c, FPG, TyG-BMI index, and TG were independent risk factors for adverse pregnancy outcomes in advanced-age GDM patients, while HDL-C was a protective factor. The ROC results showed that the AUC of the TyG-BMI index combined with TG and HDL-C was 0.897, with a sensitivity of 90.0% and a specificity of 83.8%, which were all significantly higher than those of the individual indicators. Conclusion The TyG-BMI index combined with blood lipid levels has high predictive value for pregnancy outcomes in advanced-age pregnant women with GDM.