INTRACYTOPLASMIC SINGLE SPERM INJECTION OF 1-DAY-OLD UNFERTILIZED HUMAN OOCYTES

Although the average fertilization rate in most in-vitro fertilization (IVF) centres is approximately 60-70%, there are cases of complete or virtually complete fertilization failures. The aim of our work was to study the fertilization and the subsequent cleavage characteristics o f 1-day-old human oocytes treated by intracytoplasmic single sperm inj ection (ICSI) after failing to fertilize during the standard IVF proce dure. A total of 115 metaphase II 1-day-old unfertilized oocytes were collected from 23 patients. No additional treatment was applied to the oocytes or to the semen sample. A single spermatozoon from the patien t's husband was injected into the cytoplasm of each of these oocytes 2 1-33 h after ovum retrieval. Injected oocytes were observed at 16-18 h and again 42-44 h after the ICSI procedure. Of the injected oocytes, 92% (n = 106) were intact after ICSI, 38% (n = 44) had two distinct pr onuclei and there was no difference in the fertilization rate of oocyt es when andrological and non-andrological patients were compared. Simi larly, there was no difference in the fertilization rate after ICSI wh ere patients with acceptable or good (> 15%) fertilization after stand ard IVF were compared to patients who had poor (less-than-or-equal-to 15%) fertilization after IVF. There was no significant difference in t he sperm concentration or in the progressive forward motility (a + b m otility) in these groups except where a + b motility of andrological a nd non-adrological patients was compared. The majority (84%) of the no rmally fertilized oocytes cleaved and most (77%) of these embryos show ed < 20% fragmentation 2 days after the ICSI procedure. From this stud y it can be concluded that 1-day-old metaphase II oocytes which have f ailed to be fertilized after standard IVF procedure can be fertilized and cleave when ICSI is performed on them the day after oocyte retriev al.