EFFECTS OF SPERM VIABILITY ON FERTILIZATION AND EMBRYO CLEAVAGE FOLLOWING INTRACYTOPLASMIC SPERM INJECTION

Purpose: In the human, intracytoplasmic sperm injection is typically p erformed using ''viable'' sperm which has been mechanically rendered n onmotile. The purpose of the present study was to determine the abilit y of nonviable sperm to fertilize human oocytes and the early developm ental normalcy of the resulting embryos. Methods: In this study, immat ure, prophase I oocytes from a total of 27 consenting patients were ma tured in vitro and then randomized into two groups: injection with a v iable human sperm or injection with a sperm rendered nonviable by free ze-thawing in liquid nitrogen. The rates of fertilization and cleavage were compared between the two groups. Results: The results demonstrat ed a significantly higher two-pronuclear fertilization rate when oocyt es were injected with viable sperm (62.2%) compared to when oocytes we re injected with nonviable sperm (16.2%). Oocytes injected with viable sperm also demonstrated a higher cleavage rate (91 vs 33%). Conclusio ns: These findings suggest that while the intracytoplasmic injection o f nonviable human sperm can result in normal fertilization, it does so at a much reduced rate compared to viable sperm and may not result in normally cleaving embryos.