Cryopreservation (freezing) of embryos (fertilized eggs) is utilized when the number of embryos produced during an IVF cycle exceeds the number of embryos placed in the uterus on day three or five embryo transfer. Once frozen, these embryos may be thawed and transferred in another cycle at a later time.

Gamete cryopreservation (freezing) is used to freeze sperm so that it can be used at a later time.