Correlation Between Serum Kisspeptin Levels and Pregnancy Outcomes in Frozen Embryo Transfer Cycles in Polycystic Ovary Syndrome Patients

Background: Kisspeptin, a key regulator of the hypothalamic-pituitary-ovarian (HPO) axis through GnRH stimulation, is implicated in polycystic ovary syndrome (PCOS) pathogenesis via HPO axis dysregulation. Although follicular kisspeptin levels predict success in fresh IVF cycles, their prognostic value in PCOS patients undergoing frozen-thawed embryo transfer (FET) cycles remains unknown. This study investigated the correlation between serum kisspeptin levels on the day of embryo transfer and pregnancy outcomes in patients with PCOS undergoing FET cycles. Methods: 80 PCOS patients undergoing their first FET cycle were prospectively enrolled. Patients were divided into three groups based on the tertiles of serum kisspeptin levels on the day of embryo transfer. The relationship between serum kisspeptin levels and pregnancy outcomes was analyzed. Multivariate logistic regression analysis was conducted to adjust for potential confounders, and a restricted cubic spline model was employed to examine the dose-response relationship between kisspeptin levels and pregnancy outcomes. Results: There were no significant differences in baseline characteristics among the three groups, except for the basal follicle-stimulating hormone level (p < 0.001). Significant differences were observed among the three groups in terms of live birth rate, pregnancy rate, and clinical pregnancy rate. Multivariate logistic regression analysis revealed that the odds of live birth were significantly higher in the third tertile (T3) group (highest kisspeptin levels) than in the first tertile (T1) group (lowest kisspeptin levels). Restricted cubic spline analysis showed a significant dose-response relationship between serum kisspeptin levels and pregnancy outcomes. Additionally, serum kisspeptin levels were positively correlated with progesterone levels on the day of embryo transfer day, whereas no significant correlation was observed with estradiol levels. Conclusions: In PCOS patients undergoing frozen-thawed embryo transfer cycles, higher serum kisspeptin levels were associated with improved pregnancy outcomes, suggesting that kisspeptin may serve as a useful biomarker for predicting pregnancy success.