Embryo cryopreservation is useful for leftover embryos after a cycle of in vitro fertilization, as patients who fail to conceive may become pregnant using such embryos without having to go through a full IVF cycle. Or, if pregnancy occurred, they could return later for another pregnancy. Spare oocytes or embryos resulting from fertility treatments may be used for oocyte donation or embryo donation to another woman or couple, and embryos may be created, frozen and stored specifically for transfer and donation by using donor eggs and sperm.
Human oocyte cryopreservation (egg freezing) is a procedure to preserve a woman's eggs (oocytes).The eggs are extracted, frozen and stored. The intention of the procedure is that the woman may choose to have the eggs thawed, fertilized, and transferred to the uterus as embryos to facilitate a pregnancy in the future.
Semen cryopreservation (commonly called sperm banking or sperm freezing) is a procedure to preserve sperm cells. Semen can be used successfully indefinitely after cryopreservation. For human sperm, the longest reported successful storage is 24 years. It can be used for sperm donation where the recipient wants the treatment in a different time or place, or as a means of preserving fertility for men undergoing vasectomy or treatments that may compromise their fertility, such as chemotherapy, radiation therapy or surgery.