PURPOSE: Direct intracytoplasmic sperm injection (ICSI) is a successful treatment of severe male subfertility. Conventional in vitro fertilization shows poor pregnancy rates especially in cases of severe teratozoospermia. The objective was to determine if severe morphological defects of spermatozoa in oligoasthenoteratozoospermia (OAT) have any impact on the fertilization process in ICSI and if there are any specific morphological characteristics in nonfertilized oocytes after the ICSI procedure. METHODS: Ejaculates and nonfertilized oocytes were investigated by electron microscopy. CONCLUSIONS: The lack of intracytoplasmic sperm-oocyte interaction, not severe sperm defects, displays the most critical role in the fertilization process. Clinical data with fertilization rates of 66% and pregnancy rates of 23.3% confirm the fertilization capacity of severely
