The predictability of subnormal penetrating capacity of sperm in cases of unexplained infertility

Multivariate discriminant analysis has been used to determine the predictability of sub‐normal penetrating capacity in cases of unexplained infertility. The product of this analysis was the identification of 7 discriminating variables all of which described various aspects of the post‐capacitation movement characteristics exhibited by the spermatozoa, omitting all reference to the conventional parameters of semen quality. On the basis of these discriminating variables, 90.9% of samples exhibiting penetration rates within the normal range were correctly predicted to be functionally competent. The same variables correctly identified only 60% of samples with impaired penetrating capacity, indicating that in the remaining 40%, defects are present in the spermatozoa which are not reflected in their motility patterns.