Effects of sperm direction in Piezo-ICSI on oocyte survival, fertilization, embryo development and implantation ability in humans: A preliminary study

Aims The objective of this study was to investigate the effect of the head-first or tail-first injection of sperm into the cytoplasm by Piezo-ICSI (PICSI) on oocyte survival, fertilization, embryo development and implantation ability in humans. Methods We retrospectively investigated 632 mature oocytes retrieved from 152 infertile patients who attended our PICSI-ET program at the Niji Clinic between October 2010 and January 2014. Of these, 342 mature oocytes retrieved from 75 patients were injected with sperm head first, and 290 mature oocytes retrieved from 77 patients were injected with sperm tail first into the cytoplasm. The rates of oocyte survival, fertilization, good-quality day-3 embryos, pregnancy, implantation and live birth were evaluated in both groups. Results There were no differences among the two groups with respect to survival, fertilization, good-quality day-3 embryos, pregnancy, implantation and live birth rates. Conclusion Sperm direction (i.e., head first or tail first) does not influence the outcome of PICSI in human oocytes, including oocyte survival, fertilization, embryo development and implantation ability. These findings contribute to an understanding of factors that influence the success of human intracytoplasmic sperm injection (ICSI) techniques.