Objective To investigate the dynamic changes in metabolic and inflammatory indicators in patients with polycystic ovary syndrome (PCOS) during in vitro fertilization-embryo transfer (IVF-ET), determine the key thresholds for predicting live birth, and construct a risk stratification model.

Methods A prospective cohort study was conducted. A total of 185 PCOS patients (PCOS group) who underwent their first autologous oocyte IVF-ET cycle and 181 age-matched controls (control group) were included as the study subjects. Glycolipid metabolic indicators and inflammatory indicators were dynamically monitored at four key time points during the IVF-ET cycle. Receiver operating characteristic (ROC) curves were used to screen predictive indicators and their cut-off values, based on which a risk stratification model was constructed.

Results The comparison between the two groups at each time point showed that the levels of low-density lipoprotein cholesterol (LDL-C), fasting blood glucose (FBG), triglyceride to high-density lipoprotein cholesterol ratio (TG/HDL-C), and triglyceride-glucose-body mass index (TyG-BMI) in the PCOS group were higher than those in the control group at all time points, with statistically significant differences(adjusted P < 0.05). Except for the trigger day, the levels of triglycerides (TG) and total cholesterol (TC) in the PCOS group were higher than those in the control group at the other three time points, while the level of high-density lipoprotein cholesterol (HDL-C) was lower than that in the control group, with statistically significant differences (adjusted P < 0.05). The levels of interleukin-6 (IL-6) and interleukin-8 (IL-8) before ovulation induction in the PCOS group were higher than those in the control group, with statistically significant differences (P < 0.001). After IVF-ET stimulation, the level of IL-8 after embryo transfer in the PCOS group was also higher than that in the control group, with a statistically significant difference (P=0.015). The ROC curves showed that both post-transfer IL-8 and TyG-BMI were effective predictors of live birth, with areas under the curve of 0.839 and 0.629, respectively, and cut-off values of 50.73 pg/mL and 211.55, respectively. Based on this, a joint risk model was constructed and grouped. The live birth rate in the low-low group was 84.44%, while that in the high-high group was only 11.36%, with a statistically significant difference (χ²=45.77, P < 0.001). The live birth rate in the group with only elevated IL-8 (18.97%) was also lower than that in the group with only elevated TyG-BMI (47.37%), with a statistically significant difference (χ²=7.49, P=0.006).

Conclusion The IVF-ET process can exacerbate metabolic and inflammatory disorders in PCOS patients. The "metabolic-inflammatory turning threshold" constructed in this study has clinical early warning value and suggests that the inflammatory pathway may play a dominant role in pregnancy outcomes. It emphasizes the important value of dynamic monitoring of metabolic and inflammatory indicators for achieving individualized management.