Objective: To determine whether the performance of intracytoplasmic sperm injection (ICSI) in cases of unexplained infertility and of borderline semen parameters can prevent fertilization failure.
Design: Prospective cohort study.
Setting: Hospital-based assisted reproductive technology program.
Patient(s): Sixty couples with unexplained infertility (group 1) and 50 couples with borderline semen (group 2).
Intervention(s): Conventional IVF and ICSI were performed on sibling oocyte cumulus complexes.
Main outcome measure(s): Rate of fertilization according to patient diagnosis.
Result(s): The fertilization rate per oocyte cumulus complex in couples with unexplained infertility (group 1) was significantly higher with ICSI (65.3%) compared with IVF insemination (48.1%). Fertilization rates per OCC in couples with borderline semen (group 2) were not significantly different between ICSI (58.1%) and IVF (56.7%). In group 1, failure of fertilization after IVF insemination occurred in 10 of the 60 couples (16.7%) and in none with ICSI. In group 2, 2 of 50 couples (4.0%) failed fertilization by IVF, and 1 (2.0%) failed with ICSI. No couple in group 2 failed both IVF insemination and ICSI.
Conclusion(s): In couples with unexplained infertility, a higher fertilization rate was achieved through ICSI compared with conventional IVF. No such benefit could be demonstrated for couples with borderline semen parameters. The use of ICSI rescued 12 of 110 cycles (10.9%) where IVF failed. Adoption of the ICSI-IVF insemination split in cases of unexplained infertility may help eliminate fertilization failures.