Abstract
OBJECTIVE: To determine the most effective insemination protocol for patients undergoing emergency oocyte retrieval in natural cycles, comparing immediate denudation and intracytoplasmic sperm injection (ICSI) versus overnight culture before ICSI. DESIGN: Retrospective study comparing two insemination protocols for patients undergoing emergency oocyte retrieval in natural cycles. SUBJECTS: Reproductive Medicine Department, Affiliated Reproductive Hospital of Shandong University, from 2015 to 2021.Women undergoing natural cycle IVF treatment with emergency oocyte retrieval due to declining estradiol (E2) levels. EXPOSURE (FOR OBSERVATIONAL STUDIES): Two groups were formed based on denudation and ICSI timing. Group E underwent immediate denudation on the day of oocyte retrieval, while Group L underwent overnight culture before ICSI. MAIN OUTCOME MEASURES: Fertilization rate, high-quality embryo rate, oocyte utilization rate, and live birth rate from fresh and frozen embryo transfers. RESULTS: In this study, no significant differences were found in overall embryonic development or clinical outcomes between Groups E and Group L. However, Group L exhibited a higher fertilization rate (87.87% vs. 77.12%, P = 0.002), and Group E achieved more higher-quality embryos (52.82% vs. 40.65%, P = 0.036). The oocyte utilization rates were comparable between groups (33.61% vs. 31.98%, P = 0.702). The overall live birth rate was also similar between groups (13.33% vs. 12.5%, P = 0.88). CONCLUSIONS: These two protocols are feasible for patients in the natural cycle undergoing emergency oocyte retrieval. Group E achieved better results for fresh cycle transplantation. Group L showed a higher fertilization rate with reduced manipulation. To select protocols, clinicians should carefully consider patient-specific factors, including oocyte maturity and the clinical context.