VIABILITY OF PARTIALLY DAMAGED HUMAN EMBRYOS AFTER CRYOPRESERVATION

In our centre, embryos are judged to have survived cryopreservation if at least half of the initial number of blastomeres remain intact, The refore both fully intact and partially damaged embryos are transferred , The aim of this study was to investigate the viability of partially damaged human embryos after cryopreservation, We retrospectively analy sed the implantation and in-vivo development of embryos which were eit her fully intact or had lost some blastomeres after cryopreservation, Oocytes were collected following stimulation with the gonadotrophin-re leasing hormone (GnRH)-agonist Buserelin and human menopausal gonadotr ophin, Supernumerary multicellular embryos with not more than 20% of t heir volume filled with anucleate fragments were frozen on day 2 or da y 3 of the cycle using a slow cooling procedure with dimethylsulphoxid e as the cryoprotectant. Following slow thawing, 431 fully intact embr yos were transferred in 314 embryo transfer procedures and 488 partial ly damaged embryos were transferred in 327 such procedures, The percen tage of gestational sacs with fetal heartbeat obtained after transfer of fully intact embryos was almost three times higher than that after transfer of partially damaged embryos (11.4 versus 3.5%), Forty-five c hildren (birth rate 10% per embryo transfer) were born after transfer of fully intact embryos and 14 after transfer of embryos from which so me blastomeres had been lost following cryopreservation, In conclusion , although children have been delivered after transfer of partially da maged embryos, the aim of a cryopreservation programme must be to obta in fully intact embryos after thawing.