Objective: To evaluate the effectiveness of delayed oocyte reinsemination by ICSI (rescue ICSI) after total or near-total fertilization failure (</=25%) in IVF.
Design: A retrospective clinical study.
Setting: Non-hospital-based IVF program.
Patient(s): Thirty IVF cycles with total fertilization failure and two cycles with </=25% initial fertilization.
Main outcome measure(s): Fertilization and pregnancy rates after rescue ICSI.
Intervention(s): Rescue ICSI 19-22 hours after initial oocyte insemination.
Result(s): A fertilization rate of 60.2% was achieved with rescue ICSI (141 of 234 oocytes, 29 of 32 patients). Of 30 patients with total fertilization failure, 27 had fresh transfers with rescue ICSI embryos. Two additional patients with </=25% initial fertilization had subsequent replacement of frozen-thawed rescue ICSI embryos. Six pregnancies resulted, including three singleton, one twin, one missed abortion, and one ectopic pregnancy (20.7%). One of the singleton pregnancies resulted from replacement of four frozen-thawed embryos and is the first known pregnancy achieved from cryopreserved rescue ICSI embryos.
Conclusion(s): Rescue ICSI should be considered in the presence of total or near-total fertilization failure in IVF. Early application of rescue ICSI (19-22 hours after insemination) may be critical for establishing fertilization within an optimal window and producing viable embryos and pregnancies.