Objective: To evaluate the influence of morphology of individual spermatozoa on fertilization and pregnancy outcome.
Design: Retrospective analysis.
Setting: An IVF center in an institutional research environment.
Patient(s): Fertilization and embryo quality according to individual sperm morphology were analyzed in 662 consecutive ICSI cycles. Pregnancy outcome was evaluated for these cycles and an additional 1005 consecutive ICSI cycles.
Intervention(s): ICSI was performed using sperm cells of ejaculated, epididymal, or testicular origin. Observation through an inverted microscope was used to prospectively classify injected sperm cells as normal or morphologically abnormal.
Main outcome measure(s): Oocyte fertilization, embryo morphology, and pregnancy outcome of unmixed embryo transfers.
Result(s): Injection of morphologically abnormal spermatozoa (irrespective of origin) resulted in a lower fertilization rate (60.7%) than did injection of morphologically normal spermatozoa (71.7%). Embryo cleavage quality did not differ between groups. Higher pregnancy and implantation rates were obtained in patients with normal sperm morphology (36.7% and 18.7%, respectively) than in those with abnormal sperm morphology (20.2% and 9.6%).
Conclusion(s): Individual sperm morphology assessed at the moment of ICSI correlated well with fertilization outcome but did not affect embryo development. The implantation rate was lower when only embryos resulting from injection of an abnormal spermatozoon were available.