Sperm morphology assessment as an indicator of human fertilizing capacity.

Semen samples from 95 men were examined by routine semen analysis and specific histologic staining for sperm morphology. The men were classified into fertile and infertile groups on the basis of clinical evaluation and in vitro testing, using the zona-free hamster egg penetration assay. Thirty men were designated as fertile, as they had fathered children and their sperm showed penetration of greater than 20% of the zona-free hamster eggs with the in vitro fertilization test. Subjects classified as infertile were men from infertile couples whose wives showed no evidence of infertility and whose in vitro fertilization ability was 10% or less. The semen analysis parameters of the fertile and infertile groups were significantly different. Fertile men had mean values of 108 X 10(6) sperm/ml, 61% motile, 64% normal forms (sperm with oval morphology), and 69% penetration in vitro. The mean values for infertile men were significantly lower: 42 X 10(6) sperm/ml, 45% motile, 32% normal forms, and 3.2% penetration in vitro. The importance of the morphology parameter was revealed by comparison of the percentage of penetration with count, motility, and morphology. Penetration correlated best with morphology (r = 0.730) as compared with motility (r = 0.451) and count (r = 0.605). The distribution of abnormalities in the infertile group revealed 81.6% with abnormal morphology (less than 50%), 53.8% with abnormal motility (less than 50%), and 38.5% with abnormal count (less than 20 million/ml). As a single parameter, decreased number of normal forms appears to be a good indicator for clinical infertility if in vitro fertilization testing is not available.