[Association between progesterone levels on the day of ovulation and pregnancy outcomes in patients with normal ovarian response undergoing natural cycle frozen embryo transfer].

This study explored the influence of progesterone (P) levels on the day of ovulation on pregnancy outcomes in patients with normal ovarian response undergoing natural-cycle frozen-thawed embryo transfer. A total of 384 natural-cycle frozen-thawed embryo transfer cycles of patients with normal ovarian response treated at the Reproductive Medicine Center of Beijing Obstetrics and Gynecology Hospital, Capital Medical University, from August 2022 to December 2024 were retrospectively enrolled in the study. Subjects were divided into Group A (P≤1 μg/L), Group B (1 μg/L<P≤3 μg/L), and Group C (P>3 μg/L) based on serum progesterone concentrations on the ovulation day. Baseline clinical data and pregnancy outcomes were compared across the three groups, and the effects of ovulation-day progesterone levels and other clinical indicators on pregnancy outcomes were statistically analyzed. Group A consisted of 94 patients with a mean age of (31.2±5.4) years; group B included 173 patients with a mean age of (30.4±5.9) years; group C comprised 117 patients with a mean age of (30.8±5.2) years. The results showed that Group B had a clinical pregnancy rate of 55.5%(96/173)and an embryo implantation rate of 46.1%(118/256), which were significantly higher than those of Group A [39.4%(37/94)and 31.5%(45/143)] and Group C [46.2%(54/117)and 37.1%(63/170)], with statistically significant intergroup differences (P<0.05). Multivariate logistic regression after adjustment for confounding variables verified that ovulation-day progesterone level was an independent risk factor for clinical pregnancy (OR=1.27, 95%CI: 1.10-1.45, P=0.001), while BMI acted as a protective factor for clinical pregnancy (OR=0.93, 95%CI: 0.87-1.00, P=0.037). In conclusion, progesterone level on the day of ovulation serves as a crucial indicator affecting clinical pregnancy outcomes of natural-cycle frozen-thawed embryo transfer, and routine monitoring of this parameter in clinical practice is conducive to optimizing transplantation protocols and improving the overall clinical pregnancy rate.