PROSPECTIVE, AUTO-CONTROLLED STUDY ON REINSEMINATION OF FAILED-FERTILIZED OOCYTES BY INTRACYTOPLASMIC SPERM INJECTION

Objective: To evaluate the possible influence of late fertilization after standard IVF on the results of reinsemination of assumed failed-fertilized oocytes by microinjection and to examine the correlation between the effect of aging of (failed-fertilized) oocytes and the ability of these oocytes to become fertilized. Design: Trial 1: Group 1 (injected-day 1), 93 failed-fertilized oocytes injected 1 day after ovum pick-up; group 2 (control), 82 failed-fertilized oocytes with no microinjection performed. Trial 2: Group 1 (ICSI-day 1), 40 failed-fertilized oocytes injected 1 day after ovum pick-up; group-2 (ICSI-day 2), 40 failed-fertilized oocytes injected 2 days after ovum pick-up. In addition, 35 two- to eight-cell stage embryos, obtained after ICSI of IVF failed-fertilized oocytes, were fixed for cytogenetic analysis. Main Outcome Measures: Normal and abnormal fertilization and embryo development. Results: Trial 1: 53% normal (2 pronuclear [PN]) and 25% abnormal (greater than or equal to 3PN) fertilization rates were obtained in group 1 (injected-day 1), and 71% of the 2PN and 74% of the greater than or equal to 3PN oocytes cleaved with <50% fragmentation. No pronuclear (greater than or equal to 2PN) development occurred in the control group. Trial 2: 45% and 8% normal and 25% and 40% abnormal fertilization rates were obtained, respectively, after ICSI of 1-day-old and 2-day-old failed-fertilized oocytes. Two days after microinjection, 67% and 67% of the 2PN and 80% and 44% of the greater than or equal to 3PN oocytes cleaved with <50% fragmentation in group ICSI-day 1 and in group ICSI-day 2, respectively. Conclusions: Late fertilization after initial in vitro insemination does not play a role in the high fertilization rate obtained after reinsemination of assumed failed-fertilized oocytes by ICSI. Normal (2PN) fertilization rate, however, decreases strongly and the abnormal (greater than or equal to 3PN) fertilization rate increases with oocyte aging and derived embryos seem to have a high incidence of cytogenetic abnormalities.