Objective: To analyze the impact of serum progesterone (P) levels on HCG Trigger Day on the Outcomes of fresh high-quality embryo transfer in GnRH antagonist cycles.
Methods: This retrospective study analyzed 380 patients undergoing fresh cycle high-quality embryo transfer with antagonist protocol at Southwest Medical University reproductive center (January 2019-December 2024).All the included patients were categorized into three groups based on serum P levels on HCG day:Group A (P ≤ 0.8 ng/mL), Group B (0.8＜P≤1.0 ng/mL), Group C(P >1.0 ng/mL). Based on the POSEIDON criteria, patients were stratified into subgroups for further analysis: expected poor ovarian responders (Group 3/4) and unexpected poor ovarian responders (Group 1/2), each divided by progesterone levels (≤0.8 vs >0.8 ng/mL) on HCG day. The reproductive outcomes were compared among the three groups and subgroups.Ordinal logistic regression analyzed factors influencing hCG-day P levels.