Background: Sperm immobilization is an important step in intracytoplasmic sperm injection (ICSI) as it is necessary for oocyte activation by the spermatozoa. Several techniques are available for sperm immobilization. However, the effects of sperm mobilization techniques on intracytoplasmic sperm injection outcomes have not been established as most of the reports of studies on sperm immobilization techniques are inconsistent. This study aimed to evaluate a mild aggressive mechanical sperm immobilization technique: micro-rubbing, and investigate the effectiveness of micro-rubbing sperm immobilization in ICSI.
Methods: Matched retrospective cohort study of patients who underwent intracytoplasmic sperm injection between April 2018 and June 2023 were enrolled. Non-preimplantation preimplantation genetic testing (non-PGT) and preimplantation genetic testing for aneuploidy (PGT-A) cycles were categorised into two groups based on sperm immobilization method: micro-rubbing and single-touch. Each couple was matched with separate control patients treated by the same operator for ICSI and oocyte denudation, maternal age, duration of infertility, primary or secondary infertility, sperm source, embryo condition, and endometrial thickness on the day of embryo transfer. Main Outcome Measures included: fertilization, oocyte utilization, and blastocyst chromosomal aneuploidy rates.
Results: Overall, 2967 ICSI cycles were evaluated, of which 330 and 318 cycles performed using micro-rubbing sperm immobilization in non-PGT and PGT-A groups, respectively. Compared with the ICSI cycles performed using single-touch sperm immobilization, micro-rubbing sperm immobilization cycles have significantly higher fertilization (non-PGT: 85.28% vs. 76.06%, P < 0.001; PGT-A: 85.26% vs. 75.45%, P < 0.001), day-3 embryo utilization per 2 pronucleus, and embryo utilization rate on day 3 per oocyte injected (non-PGT: 64.13% vs. 50.24%, P < 0.001; PGT-A:63.43% vs. 48.79%, P < 0.001). There were no statistically significant differences in embryo cleavage, top-quality embryos on day 3, blastocyst formation, blastocyst chromosomal aneuploidy, implantation, pregnancy, live birth, or miscarriage rates between both groups.
Conclusions: Micro-rubbing sperm immobilization appears to be effective, with a statistically significant improvement in fertilization and embryo utilization rate on day 3 per oocyte injected. However, it does not seem to affect clinical pregnancy or live birth rates per transfer.
Keywords: Fertilization; ICSI; Micro-rubbing; Oocyte utilization; Sperm immobilization.
© 2025. The Author(s).