Clinical assisted reproduction: Cryopreservation of embryos, blastocysts, and pregnancy rates of blastocysts derived from frozen-thawed embryos and frozen-thawed blastocysts

To evaluate the development of cryopreserved embryos when thawed and subsequently cultured to the blastocyst stage in comparison to transferring cryopreserved blastocysts. In this retrospective clinical study, we have evaluated 170 cycles in patients undergoing IVF treatment for infertility. Cryopreserved embryos were thawed and were subsequently cultured and transferred at the blastocyst stage. Cryopreserved blastocysts (Day 6) were thawed and transferred immediately. Five hundred and sixty embryos and 444 blastocysts have been thawed. In the embryos group, the survival rate was 89% while in the blastocyst group the survival rate was 56%. In the embryos group the blastocyst development rate was 24.5%. The implantation rate in the embryos group was 20.6% per group blastocyst transferred compared to 5.3% in the blastocyst group. The ability of cryopreserved embryos to develop to blastocysts and their implantation potential does not seem to be greatly affected by the cryopreservation procedure.