Cryopreservation is the process of freezing and storing embryos for transfer later. Freezing of Embryos gives couples the opportunity to try additional cycles of IVF, either after a failed attempt, or a first birth or even after medical treatments such as chemotherapy. In a single IVF cycle, a large number of embryos are sometimes produced. When transferring embryos back into the uterus we try to avoid twin/triplet pregnancy, and therefore more than 3 embryos are rarely transferred. Thus, at the end of a treatment cycle, extra embryos may be frozen and used in the future in case the patient does not conceive or if she returns for treatment again after completing her pregnancy.
Freezing is done with the aid of an embryo freezer and the embryos are frozen in straws and transferred into liquid nitrogen dewars.