In vitro fertilization in couples with male factor infertility.

The data from 83 consecutive in vitro fertilization-embryo transfer cycles were examined with emphasis on the presence of subfertile male parameters, including abnormal sperm density, motility, morphologic features, or an abnormal result in the sperm penetration assay (zona-free hamster ova penetration). There were 25 cycles (21 couples) in which there was a solitary or coexistent abnormal male factor. The presence of a male factor was associated with a lower fertilization rate and fewer embryos transferred. Statistically important reductions in the fertilization rate occurred with reduced sperm density and abnormal motility, but not with abnormal morphologic features. The parameter that was most significantly associated with human ova fertilizability was the ability to exceed two penetrations per egg in the sperm penetration assay.