Sperm penetration assay and subsequent pregnancy: a prospective study of 74 infertile men.

Seventy-four men of infertile couples, for whom a female infertility factor had been excluded, were followed for up to three years after semen analyses that included the sperm penetration assay, an in vitro test of sperm function. At 156 weeks after a normal sperm penetration assay, the cumulative pregnancy rate was 68%, versus only 27% when an abnormal assay was noted. Cumulative pregnancy percents at one year varied significantly (P less than .02) according to the magnitude of the assay result (0%, 1-10%, 11-15%, 16% or greater). However, differences between 0% versus 1-10%, and 11-15% versus 16% or greater, were not statistically significant. Only one of 14 men effected conception after an assay result of 0%. These findings were little altered when analysis of the sperm penetration assay was restricted to men with normal sperm concentration (20 X 10(6) sperm mL-1 or greater) and motility (60% or greater). The presence of pyospermia (six or more white blood cells per 100 spermatozoa) was associated with continued infertility, but neither abnormal sperm concentration nor motility were associated significantly with lower cumulative pregnancy percents. When performed for infertile men according to standard protocol, the sperm penetration assay enhances prediction of future pregnancy.