OBJECTIVE: Was to determine if severe morphological defects of spermatozoa in Oligo-Astheno-Teratozoospermia (OAT) have any impact on the fertilization process in intracytoplasmic sperm injection (ICSI) and, if there are any specific morphological characteristics of unfertilized oocytes after the ICSI procedure. METHODS: Ejaculates of males with severe subfertility and unfertilized oocytes after the ICSI procedure were investigated by transmissionelectronmicroscopy. RESULTS: ICSI provided a fertilization rate of 66% in cases of severe defective spermatozoa. The ultrastructure revealed severe head and neck alterations in particular. The ultrastructure of the unfertilized oocyte displayed mostly no signs of activation and lack of decondensation of sperm chromatin. CONCLUSIONS: Our findings support the hypothesis that not severe sperm defects but the lack of intracytoplasmic sperm-oocyte interaction displays the most critical role in the fertilization process in intracytoplasmic sperm injection.
