In vivo and in vitro decondensation of human sperm and assisted reproduction technologies

For a successful fertilization and pronucleus formation to occur, not only a properly condensed sperm nucleus, but also decondensation ability in the oocyte is important. The sperm abnormalities causing failure of sperm decondensation in the oocyte are unrecognizable by conventional semen analysis and different methods are used. The chromatin decondensation ability of the human spermatozoa in vivo and in vitro and its association with infertility and assisted reproduction techniques (ART) are clearly discussed in this paper. The factors affecting the decondensation ability of the human sperm are also mentioned. It is suggested that the methods currently used to assess sperm chromatin decondensation are of limited value in assessing fertilization and pregnancy rates after ART.