A comparison of headfirst and tailfirst microinjection of sperm at intracytoplasmic sperm injection

Abstract

To investigate whether the direction of sperm loading and exit from the injection pipette during intracytoplasmic sperm injection (ICSI) had any bearing on ability to cause fertilization or affect subsequent embryonic development. Prospective randomized trial. Hospital-based IVF center. Twenty-five couples participating in an intracytoplasmic sperm injection (ICSI) program. Sperm microinjection was randomly divided into either headfirst injection or tailfirst injection. Fertilization, embryo quality, and implantation rates. There were no significant differences in the fertilization rates or the proportion of good-quality embryos, according to the direction of sperm injection. Of the embryos selected for transfer, 41.3% originated from headfirst sperm injection, and 58.7%, from tailfirst sperm injection. After transfer of either two or three embryos into 24 patients, 11 embryos implanted, with an equal probability that these embryos originated from either headfirst or tailfirst sperm injection. However, one dizygotic twin pregnancy was traced to the transfer of two embryos; one resulted from headfirst sperm injection, and one from tailfirst sperm injection. The direction of sperm microinjection at ICSI appears to have no effect on fertilization or subsequent development. The preliminary findings of this study have some interesting practical implications for the procedure of ICSI.