The freezing of oocytes and embryos is carried out by ultra-rapid freezing called nitrification. This method has many advantages over the slow freezing used until then. The excellent success rates after nitrification and freezing time are two of its advantages.
Thanks to this technique, the embryos are preserved for later use, for treatment of the couple, or to give them to other couples or to research, this is called embryo reception. Embryos are frozen at 196 degrees Celsius in liquid nitrogen until the woman or couple decides to use them. They can be kept indefinitely without losing their characteristics. Thus, embryos can be used months or years later to get pregnant.