FERTILIZING ABILITY OF SPERM WITH UNEXPLAINED IN-VITRO FERTILIZATION FAILURES, AS ASSESSED BY THE ZONA-FREE HAMSTER EGG PENETRATION ASSAY -ITS PROGNOSTIC VALUE FOR SPERM-OOLEMMA INTERACTION

Objective: To investigate the fertilizing ability of sperm with previo us unexplained IVF failure using the zona-free hamster egg penetration assay. Design: Three hundred ninety-six tests were performed after mu ltiple IVF failures. In a subsequent prospective study, 38 IVF attempt s using the microdrop insemination technique and 81 subzonal inseminat ions (SUZI) were performed. One hundred thirty-two tests with donor sp erm were carried out as controls. Patients: Three hundred fifty-two pa tients who had a minimum of two unexplained IVF failures including at least 10 metaphase II oocytes were included in the study. Results: The ability of the patient sperm to bind to hamster oocytes was lower tha n that of controls. The largest differences were the percentage of ooc ytes with swollen sperm heads and the mean number of decondensed sperm heads per penetrated oocyte: both were much lower for patients than c ontrols. Patients with a test result nil did not fertilize any oocytes during the SUZI cycles (n = 7; 50 oocytes), and the post-SUZI fertili zation rate for patients with a test value <10% was significantly lowe r than that of others (5.4 +/- 10.3 versus 23.8 +/- 8.4, respectively) . Conclusions: The defect of sperm involved in IVF failures is mainly a reduction of their fusiogenic ability and not their ability to recog nize and bind to the oolemma. Patients with a test result <10% had a s ignificantly reduced post-SUZI fertilization rate. A test score of zer o indicates a major and permanent impairment of the sperm fusiogenic a bility.