The application of the zona-free hamster egg test for the prognosis of human in vitro fertilization.

The zona-free hamster egg test was carried out using spermatozoa from 15 men which consistently failed to fertilize their wives' oocytes in vitro. Spermatozoa from nine of these men fertilized hamster eggs in vitro, indicating that positive results in this assay are an unreliable guide to human in vitro fertilization. Donor spermatozoa were needed to fertilize the wife's oocytes in three of these cases. Nevertheless, the proportion of hamster egg penetration was significantly lower compared with spermatozoa from 15 men who could fertilize their wives' oocytes in vitro. The hamster assay also failed to indicate the establishment of pregnancy.