CLINICAL FACTORS FOR SUCCESSFUL CRYOPRESERVED-THAWED EMBRYO-TRANSFER

Purpose: To study how clinical factors such as embryo quality, cell st age of embryo at cryopreservation, and synchronization of developmenta l stages between embryo and endometrium at thawing affect the implanta tion rate after cryopreserved-thawed embryo transfer (ET), these facto rs were examined in 106 cryopreserved-thawed ETs including 204 embryos . Results: In 86 embryos graded as high quality before transfer by mor phological evaluation, 31 implantations were successful, while the oth er; low-quality embryos did not implant at all. High-quality embryos r eceived less cryoinjury during cryopreservation compared to the injuri es sustained by embryos in moderate and poor quality When cyopreservat ion was performed at the 1-, 2-, and 3-day cell stages, pregnancies we re similarly achieved among most of the embryos at all cell stages. At thawed ETs in natural ovulation cycles, there were some differences a mong the developmental stages between thawed embryo and endometrium th at received the thawed transferred embryos, Although the transfer time lag ranged a day or more, asynchronism of endometrium growth to the ce ll stage did not reduce pregnancy rates. Conclusions: These results in dicated that embryo quality evaluated morphologically was the most imp ortant clinical factor for successful implantation of cryopreserved-th awed ET.