Rescue ICSI of Total Unfertilized Oocytes of Conventional IVF Cycles

[Objective] To evaluate the effectiveness of delayed oocyte reinsemination by ICSI (rescue ICSI) after total fertilization failure in IVF. [Methods] In the total of 499 IVF-ET cycles from August 2001 to August 2005, there were 25 cycles with total fertilization failure and received rescue ICSI, which named rescue ICSI group. A control group with a total of 179 cycles undergoing ICSI during the same period was named ICSI group. [Results] There was no significant difference in oocyte recovery or mean serum estradiol level of HCG day between the two groups. A fertilization rate of 57.7% was achieved in rescue ICSI group, compared to 67.8% in the control group (P 0.01). Likewise, the mean number of embryos obtained per cycle was significantly higher in the control group. The proportion of embryos that more than 4 cell on day 2 after ICSI was significantly lower in rescue ICSI group. The fragmentation and grade of embryo, however, was comparable in both groups. In addition, the pregnancy rate in the control group was 38.5%. Although there was no pregnancy obtained in rescue ICSI group, there were 2 clinical pregnancies resulted among eight patients who underwent ICSI in the following cycles. [Conclusions] Although unfertilized oocytes after IVF can be fertilized by rescue ICSI, the developmental potential of the ensuing embryos is very poor; therefore, the clinical value of rescue ICSI needs to be further studied. In addition, ICSI should be recommended in the following cycles for such patients.