Evidence that sperm with low hypoosmotic swelling scores cause embryo implantation defects

A previous prospective study using matched samples found that sperm with low hypoosmotic swelling (HOS) scores had no adverse effect on fertilization rates but markedly reduced pregnancy and implantation rates. The present study attempted to corroborate or refute the aforementioned study by comparing pregnancy rates in donor-recipient pairs using shared oocytes where the sperm of one of the two males had low HOS scores. The results found no pregnancies from the sperm with low HOS scores versus a 41% live delivered rate for those with normal scores. However, fertilization rates were not affected. This retrospective study thus confirms that sperm with low HOS scores cause implantation defects of the embryos that are formed without affecting fertilization rate, embryo cleavage rate, or embryo quality.