Subnormal sperm parameters in conventional semen analysis are associated with discrepancies between fertilization and pregnancy rates in in-vitro fertilization and embryo transfer.

Three hundred and twenty-eight consecutive treatment cycles in 168 couples were analysed retrospectively in order to examine the influence of conventional semen analysis results on the outcome of in-vitro fertilization and embryo transfer with respect to the occurrence of both fertilizations and pregnancies. All treatments were performed under maximally standardized and controlled conditions. Each of the three main determinants of the spermiogram, namely the concentration, motility and morphology of sperm in seminal plasma, was of significant importance for fertilization and subsequent pregnancy. Best correlations were achieved by counting the number of progressively (a+b) motile sperm and the number of normally formed sperm in seminal plasma. The pregnancy rate was reduced significantly in cases in which the sperm concentration was < 10 x 10(6) ml-1 (P < 0.01), or in which there was < 40% progressively motile sperm (P < 0.001), or < 30% normally formed sperm (P < 0.001). If more than one parameter in the spermiogram was abnormal, the fertilization rate depended mainly on the most disturbed sperm parameter. The implantation rate as well as the pregnancy rate was reduced significantly in patients with low progressive sperm motility and normal morphology rates. The difference could only be attributed partially to the lower number of embryos replaced. In conclusion, subnormal sperm quality seems to interfere with developmental stages beyond the process of fertilization.