Inm-5: Outcomes of Human Vitrified Embryos Transfer

The techniques of cryopreservation let embryos which cannot be immediately transferred to the patient be stored for future use. The first successful pregnancy after transfer of cryopreserved human embryos was described in 1983 by Trounson et al. and the first birth after cryopreservation was later reported in 1984 by Zeilmaker et al.). The technique has rapidly been applied in most in-vitro fertilization (IVF) programmes and a large number of children have been born. For a long time, slow cooling was the predominant method for cryopreservation of human embryos, however, vitrification has naturally become the preferred method in recent years. The first birth after transfer of vitrified human embryos was reported at Royan institute in 2008. Vitrification has been successfully utilized in freezing human oocytes as well as cleavage-stage human embryos and human blastocyst-stage. One of the draw backs of traditional slow freezing is the formation of intracellular ice, which can result in cell damage. Vitrification is an ultrarapid method of cooling cells into a glass-like state, which prevents ice crystal formation and as a result it reduces associated cell injuries. However, for achieving these results, higher concentrations of cryoprotectants must be utilized. Many published reports have indicated better post-thawing survival rates and encouraging pregnancy rates when compared with slow freezing. Although vitrification is now used widely in assisted reproduction technology (ART) clinics, there are still concerns considering the safety of vitrification. Most published reports looking at the neonatal outcomes after transfer of vitrified embryos have used blastocyst-stage embryos. Reported data on children born after transfer of Day 3 vitrified embryos are relatively rare. Our data suggest that the vitrification process did not seem to adversely influence fetal development and no increased perinatal risk was found. Long-term follow-up studies are needed to assure that there are no late consequences for the children conceived from cryopreserved and thawed embryos.