In vitro fertilizing capacity of human spermatozoa with the use of zona-free hamster ova: interassay variation and prognostic value.

The average fertilization percentage, with the use of zona-free hamster ova, of a donor group was 54% (range 11% to 100%). Nineteen sperm suspensions (24%) from a group of 79 infertile patients with semen abnormalities and 23 from a second group of 43 patients (54%) whose partner showed evidence of reproductive dysfunction, fertilized as well as spermatozoa from fertile donors. The interassay variation of the fertilization rates was found to be less than 20%. Spermatozoa from 10 patients with normal semen characteristics failed to penetrate. Six spontaneous conceptions were reported in the first group. Sperm from four of these patients had low fertilization percentages. This indicates that fertility prognosis cannot be made on the basis of a low in vitro fertilization percentage only. The fertilization rate negatively correlated with the duration of infertility. No positive assays were found after 6 years of infertility.