Egg Freezing, Embryo Freezing
Egg and embryo cryopreservation have become routine procedures in human assisted reproduction and oocyte cryopreservation is being introduced into clinical practice which is getting more and more widely used. The ability to freeze (Cryopreserve) and store for long periods of time, human sperm, embryos and recently eggs has opened many options for both fertile and infertile people. The modern freezing techniques are not associated with any significant damage to these cells as the results after thawing are very similar to those obtained with fresh ones. This allows Banking of eggs and embryos for future use. Vitification is the most popular and up-to-date embryo cryopreservation that is an ultra-rapid method of cryopreservation whereby the embryo is transitioned from 37 to −196 °C in <1 s, resulting in extremely fast rates of cooling. High concentrations of cryoprotectants together with rapid cooling rates are essential to cryopreserve embryos in a vitrified, glass-like state without any ice crystals forming. This is important in the embryology world because ice crystal formation can be very damaging to frozen embryos by reducing their viability.
There can be wide variation in the percentage of eggs that survive freeze and thaw process. It is possible that no eggs will survive the freeze and thaw process at all. Eggs are kept in liquid nitrogen tank until thawing is performed. Eggs can theoretically be stored for years and viable after thawing. This procedure is ideal for women who facing chemotherapy for cancer treatment since eggs in their ovaries will become damaged after chemotherapy. So preserving their fertile eggs prior to chemotherapy will be the only way to preserve their fertility. Fertility of women become lower as they grow older, after 35 years of age, their fecundity begins to be lower and after 40 years of age, it will be difficult to get pregnant. Freezing eggs at younger age is the way to prevent age barrier and maintain the good chance of pregnancy