Background <p>Although insulin resistance has been associated with unfavorable pregnancy outcomes, the ability of non-insulin-based insulin resistance indicators to predict adverse pregnancy outcomes has yet to be thoroughly understood. The study aims to investigate the association and predictability of triglyceride glucose-body mass index (TyG-BMI), a biomarker of non-insulin-based insulin resistance, with the risks of adverse pregnancy outcomes.</p> Method <p>The retrospective study included 1,136 subjects. Group-based trajectory modeling (GBTM) was employed to identify the TyG-BMI index trajectory. Logistic regression, restricted cubic spline (RCS) regression, and subgroup analysis were used to assess the association between the TyG-BMI index trajectory and the first-trimester TyG-BMI index with the risks of adverse pregnancy outcomes. Receiver-operating characteristic (ROC) curve analysis and the DeLong test were utilized to evaluate the prediction ability of the first-trimester TyG-BMI index for adverse pregnancy outcomes.</p> Results <p>GBTM revealed three distinct trajectories of the TyG-BMI index. Using the “low-stable” trajectory as a reference, the “high-stable” trajectory was independently associated with an increased risk of gestational diabetes mellitus (GDM) (aOR = 2.01, 95% CI 1.20–3.37), hypertensive disorders of pregnancy (HDP) (aOR = 6.05, 95% CI 3.00–12.18), and large for gestational age (LGA) (aOR = 2.83, 95% CI 1.28–6.25). The highest quartile of the first-trimester TyG-BMI index was independently linked to elevated GDM (aOR = 3.27, 95% CI 1.92–5.59), HDP (aOR = 9.26, 95% CI 3.19–26.88), and LGA (aOR = 2.26, 95% CI 1.00–5.09)risks. Additionally, the third quartile of the first-trimester TyG-BMI index had 2.21-fold increased odds of GDM (aOR = 2.21, 95% CI 1.27–3.82). The first-trimester TyG-BMI index demonstrated a significant linear association with GDM, HDP, SGA, and LGA risks. Compared to the TyG-BMI index trajectory, the highest quartile of the first-trimester TyG-BMI index exhibited a stronger association with the risks of GDM and HDP (aOR = 3.09 and 7.39, respectively). Furthermore, according to the ROC curve, the first-trimester TyG-BMI index outperformed the TyG index and triglyceride/high-density lipoprotein cholesterol (TG/HDL-c) ratio at predicting HDP (0.726 [0.650–0.801] vs. 0.603 [0.527–0.679] vs. 0.615 [0.537–0.693]), LGA (0.619 [0.540–0.699] vs. 0.534 [0.454–0.613] vs. 0.540 [0.458–0.622]), and GDM (0.664 [0.622–0.705] vs. 0.632 [0.588–0.676] vs. 0.604 [0.560–0.649]). According to the DeLong test, the first-trimester TyG-BMI index was a more valuable predictor for LGA and HDP compared to TyG index and TG/HDL-c ratio.</p> Conclusion <p>Higher levels of first-trimester TyG-BMI and a “high-stable” trajectory were linked to a greater risk of adverse pregnancy outcomes. Furthermore, as compared to TyG and TG/HDL-c, the first-trimester TyG-BMI index is a valuable predictor for HDP, GDM, and LGA.</p>