Sperm head ultramorphology and chromatin stability of males with unexplained infertility who fail to fertilize normal human ova in vitro.

An in vitro nuclear chromatin decondensation test, and quantitative nuclear ultramorphology analysis, were performed on 18 males judged to be infertile, by two failures in in vitro fertilization, and 16 fertile males. These two clinical groups only differed significantly in (1) the direction of their chromatin stability change, which took place 30-120 min post-ejaculation while stored in the seminal plasma, and (2) in the incidence of the hypoelongated sperm-head. Generally, the fertile male group exhibited positive chromatin stability change after prolonged storage, and low incidence of hypoelongated sperm heads, and vice versa in the unexplained infertile group. When the nuclear chromatin decondensation test and quantitative ultramorphology analysis were performed in step-wise fashion, it was possible to correctly classify 94% of the fertile cases with 6% of false-negative, and 89% of the unexplained infertile cases with 11% of false-positive. Therefore, it appears that these tests might be of benefit clinically for identifying functional properties of sperm-cells in unexplained infertile males, which cannot be detected by routine semen analysis.