Vitrification of human embryos based on the assessment of suitable conditions for 8-cell mouse embryos

Experiments were conducted to find a suitable cryoprotectant and suitable p rocedure for vitrification of 8-cell mouse embryos. The method was then app lied clinically to the cryopreservation of human embryos in our assisted re production programme. Mouse embryos were vitrified with 30 or 40% 1,2-propa nediol (PROH), dimethylsulphoxide (DMSO), ethylene glycol, glycerol, or ace tamide, each diluted with a solution containing 30% Ficoll plus 0.5 M sucro se, Embryos were exposed to the solutions for 0.5 or 2 min at 20 or 25 degr ees C, cooled in liquid nitrogen and warmed rapidly, Embryo survival was as sessed by in-vitro development, In PROH-, DMSO- and acetamide-based solutio ns, higher survival rates (29-82%) were obtained with less permeating condi tions, suggesting that these cryoprotectants are considerably toxic. In gly cerol- and ethylene glycol-based solutions, however, higher survival rates (74 and 92% respectively) mere obtained with more permeating conditions, su ggesting that these cryoprotectants are less toxic. Human embryos on days 2 -3 were vitrified in an ethylene glycol-based solution (EFS40), Survival, a ssessed by the morphology, was higher in 4-cell embryos on day 2 and 8-cell embryos on day 3 than in 2-3-cell embryos on day 2 or 2-7-celI embryos on day 3. From 18 transfers, one ended with the delivery of healthy twin babie s.