INTEREST OF CRYOPRESERVATION OF HUMAN EMB RYOS AT THE BLASTOCYST STAGE

The recent developpement of co-culture technique has permited to cryop reserve human embryos at the blastocyst stage. The aim of the present study was to compare pregnancy rates after transfers of embryos frozen at an early embryo stage (2-8 cell stage, group A; n = 175) with othe rs frozen at blastocyst stage (group B; n = 98). Our results demonstra ted that the frozen / thawed blastocyst survival is aproximately 100 % . In comparison the early embryos survival rate was 59 % (P < 0,05). M oreover, pregnancy rates / embryo transfer in group A (16,4 %) were si gnificantly improved by comparison to those observed with early embryo s (6,2 %) (P < 0,05). In conclusion, our results demonstrate that embr yo frozen / thawed at the blastocyst stage can be useful for improving pregnancy rates after cryopreservation.