Abstract
Some data suggest that some sperm are associated with a toxic product that lowers embryo implantation rates when these sperm come in contact with the zona pellucida. The possibility exists that shortening the incubation time could improve pregnancy rates. A randomized prospective study was initiated to evaluate pregnancy and implantation rates with transfer of embryos formed by conventional overnight vs short (2-h) co-incubation of sperm and oocytes. The clinical and viable pregnancy rates were 41 and 29% for conventional co-incubation versus 30 and 30% for short co-incubation. Implantation rates were also similar (17.9 vs 17.8%). Short incubation does not seem to impact any advantage over conventional co-incubation techniques in couples undergoing in vitro fertilization where the male factor is normal.