Aggressive sperm immobilization improves reproductive outcomes in patients with suboptimal semen parameters and previous ICSI fertilization failure

Intracytoplasmic sperm injection (ICSI) is the most effective procedure to resolve male infertility, enhancing overall fertilization and pregnancy outcomes. However, it is important to note that fertilization failure (FF) can still occur in a few cases after ICSI. This study aims to introduce a specialized technique of aggressive sperm immobilization for ICSI and evaluate its impact on reproductive outcomes in cases involving prior fertilization failure. All infertile couples with male partners having suboptimal semen samples and previous ICSI fertilization failure were evaluated using retrospective data from National Taiwan tertiary university hospital (NTUH) between January 2016 and February 2022. Fertilization failure in our study was defined as less than 30% fertilization rate (FR, the number of normally fertilized oocytes divided by the total number of injected mature oocytes). Data involving both standard (routine procedure) and aggressive sperm immobilization (SI) techniques during different ICSI cycles were included in this study. Standard and aggressive SI methods were performed by compressing the distal half tail of the spermatozoa ≦ 5 and 15 times prior to ICSI respectively. Generalized estimating equations analysis were applied to compare the clinical outcomes between two procedures. Overall, data from 23 infertile couples who had undergone 65 ICSI cycles (31 standard SI with low fertilization rate and 34 aggressive SI) were included in the study. The average FR in the ICSI cycles with standard SI and aggressive SI were 23.6 ± 23.1% and 49.5 ± 31.8 respectively ( P = 0.0002). The majority of embryos were transferred at the day 3 stage, with an average number transferred of 2.6 ± 0.9 in the aggressive SI group and 1.9 ± 0.9 in the standard group. The number of embryos transferred per transfer cycle was higher in the aggressive SI ( P = 0.015), whereas the number of good-quality embryos was similar between the two procedures ( P = 0.44). There were one and seven live births from the standard SI cycles and aggressive SI cycles respectively. In conclusion, aggressive SI was associated with a significantly higher FR, resulting in more available embryos for transfer without compromising embryo quality. Therefore, this specialized technique improved pregnancy outcome among infertile couples with a previous ICSI–FF. It can be a safe, economic, and effective method to improve the assisted reproductive technologies outcomes for infertile patients affected by previous ICSI–FF.