Egg freezing, technically called oocyte cryopreservation, involves stimulating, extracting, freezing, and storing a woman’s eggs (oocytes). The eggs can be thawed months, or even years, later and fertilized, creating embryos. These embryos then can be transferred to the uterus in an attempt to achieve a successful pregnancy.
Cryopreservation is not new. Since the 1950’s, human sperm has been frozen and stored, and since the 1980’s, human embryos have been cryopreserved. Both sperm and embryo freezing are routine procedures performed successfully in most fertility centers around the world.Egg freezing, however, is not yet routine. Issues in freezing and thawing of human eggs center on the high water content of the egg itself. Using conventional freezing methods, the egg is susceptible to both damage and destruction as ice crystals within the egg can cause it to fracture upon thawing. There are also safety issues concerning chromosomal abnormalities within the thawed egg.
New cryopreservation technology, called “vitrification,” has revolutionized our ability to thaw successfully frozen eggs. In vitrification, rapid cooling rates spare the egg from forming ice crystals within, and as a result, they are less likely to fracture upon thawing. Having the tools to predictably and safely thaw eggs, the stumbling blocks are removed.