High-magnification ICSI overcomes paternal effect resistant to conventional ICSI.

Previous studies have shown that repeated intracytoplasmic sperm injection (ICSI) failures can be caused by a paternal effect. Other studies have suggested that ICSI results are compromised if morphologically abnormal spermatozoa are injected into oocytes. This study was undertaken to evaluate the usefulness of a high-magnification optical system to select spermatozoa to be used for ICSI (high-magnification ICSI) in couples with repeated conventional ICSI failures. Couples with two or more previous conventional ICSI failures underwent an additional conventional ICSI attempt, followed by a high-magnification ICSI attempt. The outcomes of the two sequential attempts were compared. In 72 of these patients, sperm DNA integrity was assessed. In the whole group of 125 couples with repeated ICSI failures, high-magnification ICSI improved clinical outcomes (pregnancy, implantation, delivery and birth rates) without affecting biological outcomes (fertilization and cleavage rates, embryo morphology). The improvement of clinical ICSI outcomes was evident both in patients with an elevated degree of sperm DNA fragmentation and in those with normal sperm DNA status. It is concluded that high-magnification ICSI improves clinical outcomes in couples with previous repeated conventional ICSI failures.