Early rescue oocyte activation for activation-impaired oocytes with no second polar body extrusion after intracytoplasmic sperm injection

Purpose When rescue artificial oocyte activation (ROA) is performed on the day after intracytoplasmic sperm injection (ICSI) or later, embryonic development is poor and seldom results in live births. The efficacy of an early ROA after ICSI is unclear. Is early ROA effective in rescuing unfertilized oocytes that have not undergone second polar body extrusion several hours after ICSI? Methods We performed retrospective cohort study between October 2016 and September 2019, targeting 2891 oocytes in 843 cycles when ICSI was performed. We performed ROA with calcium ionophore on 395 of the 475 oocytes with no second polar extrusion 2.5-6 h after ICSI. Results The normal fertilization rate of ROA oocytes was significantly higher than non-ROA oocytes (65.8% vs 6.7%, P < 0.001). The blastocyst development rate in ROA oocytes was significantly lower than spontaneously activated oocytes (48.9% vs 67.2%, P < 0.001). The ROA oocyte implantation rate did not significantly differ from the spontaneously activated oocytes (36.0% vs 41.2%). We observed no differences in the implantation rates and blastocyst development rates over the 2.5-6 h from ICSI until ROA. Conclusion Early ROA is effective, and the optimal timing appears to be 2.5-6 h after ICSI.

Automated summary

The study suggests that early ROA after ICSI is effective in rescuing unfertilized oocytes, with a higher normal fertilization rate compared to non-ROA oocytes. However, the blastocyst development rate is lower, while the implantation rate is similar to spontaneously activated oocytes.