[Human embryo freezing with dimethylsulfoxide (DMSO) and sucrose as cryoprotectants]

176 supernumerary human embryos following treatment by IVF were cryopreserved with dimethylsulfoxide (1.5M) and sucrose (0.1M) as cryoprotectants. The embryos were frozen at the early cleavage stage (48-96 hours after insemination) in the programmable freezer, by means of the protocol providing for slow cooling until -40 degrees C and slow thawing. The survival rate (50% or more blastomeres were intact) after thawing was higher for the embryos at the 8 cell stage to the morulla stage (60-96 hours after insemination) than for the embryos at the 4 to 6 cell stage (48-60 hours after insemination) (87% and 66%, p < 0.001), and the overall survival rate was 80% (140/176). Out of 62 transfer cycles, 11 pregnancies (17.7%) and 6 deliveries (9.7%) were achieved. No fetal malformation or chromosomal aberration was observed.