Effects of different fertilization methods on oocyte maturity

Objective: To investigate the effects of different fertilization methods on oocyte maturity. Methods: A retrospective analysis was conducted on patients who underwent in vitro fertilization (IVF)/intracytoplasmic sperm injection (ICSI) at the Reproductive Medicine Center of The Fourth Hospital of Shijiazhuang between January 2022 and June 2024. A total of 2553 cycles were included and categorized into four groups based on medical history and fertilization strategy: Group I (1111 cycles): Short-term fertilization for patients with primary infertility (no prior pregnancy between the couple); Group II (619 cycles): Overnight fertilization for patients with secondary infertility (prior pregnancy history); Group III (584 cycles): ICSI for patients with male factor infertility; Group IV (239 cycles): Short-term fertilization combined with early rescue ICSI (Re-ICSI). The short-term fertilization group was further subdivided by observation timing: the D0 subgroup (assessed on the day of oocyte retrieval) and the D1 subgroup (assessed on the day of fertilization observation). Comparisons were performed between the D0 and D1 subgroups, D1 subgroup and overnight fertilization group, ICSI and Re-ICSI groups, and D0 subgroup and Re-ICSI group, focusing on general clinical data and oocyte maturation parameters. Results: The D1 subgroup exhibited significantly higher metaphase II (MII) and metaphase I (MI) oocyte rates, and a significantly lower germinal vesicle (GV) oocyte rate compared to the D0 subgroup ( P <0.05). The overnight fertilization group had a significantly higher female age and lower number of retrieved oocytes than the short-term fertilization group ( P <0.05), alongside a significantly higher MII oocyte rate and lower GV oocyte rate than the D1 subgroup ( P <0.05). The Re-ICSI group showed significantly fewer retrieved oocytes and lower oocyte maturity than the D0 subgroup ( P <0.05). No significant differences in oocyte maturity were observed between the ICSI and Re-ICSI groups ( P >0.05). Conclusion: Different fertilization methods exert distinct impacts on oocyte maturity, with overnight fertilization yielding the highest maturity, followed by short-term fertilization, and Re-ICSI yielding the lowest. This variation may be associated with asynchronous oocyte development.