Oocytes from women of advanced reproductive age do not appear to have an increased risk of zona pellucida hardening.

Purpose: To test the hypothesis that very advanced reproductive age leads to an increased risk of zona pellucida hardening by comparing fertilization rates and rates of failed fertilization with conventional oocyte insemination vs intracytoplasmic sperm injection (ICSI).

Methods: Women aged > or = 45 were given the option of ICSI vs conventional oocyte insemination in circumstances where there was no male factor present. They were advised of the theoretical benefit of ICSI overcoming zona hardening but also advised that ICSI might lower pregnancy rates and is more costly.

Results: There were 364 cycles evaluated and 74% chose ICSI. The failed fertilization rates were similar--28.4% (66/232) for ICSI vs 26.5% (35/132) for conventional insemination. The fertilization rates were similar 56.0% with ICSI vs 50.9% with conventional oocyte insemination.

Conclusion: Based on similar fertilization and failed fertilization rates in women aged > or = 45 undergoing IVF-ET, zona hardening does not appear to be a consequence of reproductive aging.