[Clinical experience with assisted reproductive technology along the development of micro fertilization]

In 1993 we had the first success of micro fertilization in our clinic. The method by partial opening of oocyte zona pellucida initially used achieved a fertilization rate per egg of only 26.7%. Although transfer of sperm under the zona raised the fertilization rate to 39.2%, the new method involved problems such as polyspermy, which represented approximately 30% of the total fertilization rate. In addition, use of this method was limited to patients meeting several conditions. In 1994, we had a successful case of pregnancy after intracytoplasmic sperm injection (ICSI). The ICSI method resulted in a fertilization rate of about 70%, and has solved the problem of polyspermy. Fertilization of eggs has become possible using immotile sperm, and the technique of microsurgical epididymal sperm aspiration (MESA) and testicular sperm extraction (TESE) has been established. Clinical data have confirmed that a fertilization rate by frozen sperms is not lower than that by fresh sperms. Sperm can be stored frozen after MESA or TESE and therefore are surely available when needed, allowing to avoid spoiling retrieved eggs. No difference in fertilization rate was found between conditions needing micro fertilization or sperm recovery methods. No difference in pregnancy rate was shown between treatment cycles. Recent reports show improved pregnancy rates using techniques such as transferring a frozen embryo after endometrical adjustment. Further development in assisted reproductive technology is anticipated.