Rescue ICSI of oocytes that failed to extrude the second polar body 6 h post-insemination in conventional IVF

BACKGROUND: Attempts to 'rescue' by ICSI oocytes that remained unfertilized 24 h after conventional IVF have generally resulted in poor outcomes. The aim of the present study was to compare the outcome of rescue ICSI performed on one group of patients 6 h after initial insemination with those of another group where rescue ICSI was performed 22 h after initial insemination. METHODS: Twenty-five patient IVF cycles provided the oocytes for rescue ICSI 6 h after initial insemination, and 20 cycles provided the oocytes for rescue ICSI 22 h after initial insemination in this retrospective study. Fertilization and cleavage rates, embryo quality, implantation, and pregnancy rates after rescue ICSI were the main outcome measures. RESULTS: A fertilization rate of 70.3% was achieved with 6 h rescue ICSI compared with 48.5% with 22 h rescue ICSI (P < 0.0001). From 6 h rescue ICSI, 12 clinical pregnancies (48.0%) resulted in three sets of twins, eight singletons and one abortion. From 22 h rescue ICSI there was one (5.0%) singleton pregnancy and delivery of a healthy baby. Likewise, the implantation rate was 20.2% from 6 h rescue ICSI compared with 1.72% from 22 h rescue ICSI (P < 0.02). CONCLUSIONS: Rescue ICSI after 6 h post-insemination (46 h post-HCG) gave better fertilization, pregnancy and implantation rates compared with rescue ICSI after 22 h when oocytes have become aged.