Abstract
The cryopreservation of supernumerary human blastocysts produced in vitro has been essential in assisted reproductive technology. In this case report, we report the clinical results of the transfer of expanded blastocysts that were cryopreserved by a slow-freezing method or a vitrification technique after artificial shrinkage. The post-thaw survival and re-expansion rates in the slow-freezing group (100 and 60%) were comparable with those in the vitrification group (95 and 95%). However, although no pregnancy was achieved in the slow-freezing group, high implantation and clinical pregnancy rates (44 and 60%) were achieved in the vitrification group.
