Pregnancy rates after transfer of cryopreserved blastocysts cultured in a sequential media

Objective This study was undertaken to determine the pregnancy rate after transfer of cryopreserved blastocysts. Study design Retrospective review of 61 patients from January 1, 2002, to December 31, 2003, who were transferred with blastocyst embryos cryopreserved on day 5 or 6 after culture in a sequential media. The cryopreserved blastocysts were thawed by using a 7-step dilution process after rapid thawing half hour to 2 hours before embryo transfer. Results The pregnancy rate after transfer of 61 patients with cryopreserved blastocysts was 66%, with 49% having cardiac activity. The pregnancy rate after transfer of 3 blastocysts was 71% and after transfer of 2 blastocysts was 66%. The pregnancy rate of blastocysts cryopreserved after intracytoplasmic sperm injection was 56%. Conclusion Cryopreservation and transfer of blastocysts appears to be a reliable procedure, and that the human blastocyst can be cryopreserved and thawed without a significant loss of viability