Experience with assisted fertilization in severe male factor infertility and unexplained failed fertilization in vitro.

We present results of in-vitro fertilization (IVF) cycles using assisted fertilization at our centre. Assisted fertilization was performed in those couples who had failed to fertilize oocytes with conventional IVF, or where this was predicted by the presence of severe male factor infertility. In 20 consecutive assisted fertilization cycles 223 oocytes were subjected exclusively to subzonal insemination (SUZI). Subsequently in 32 consecutive assisted fertilization cycles 418 oocytes were subjected to intra-cytoplasmic sperm injection (ICSI). More oocytes were damaged by ICSI (8.9%) than by SUZI (2.3%) (P = 0.03), but normal fertilization resulted more often after ICSI (56.9%) than SUZI (35.8%) (P = 0.004). Sperm parameters, other than sufficient numbers to perform the procedures, had no effect on fertilization or pregnancy rates. Every cycle led to the transfer of at least one embryo. Pregnancy resulted from eight of the SUZI cycles (40%) and nine of the ICSI cycles (28%). Implantation rates were calculated as 25 and 12% for SUZI and ICSI respectively. The presence of living spermatozoa is the only semen parameter limiting assisted fertilization. At present more centres are able to perform SUZI than ICSI and we feel it is premature to abandon SUZI altogether. Local conditions and success rates should be considered when decisions are made in assisted fertilization cycles.