All biological activity is paused until it is thawed. Freezing needs cryopreserving agents that minimize damage to the cells during freezing and thawing process. Semen cryopreservation also called sperm banking is a procedure to preserve sperm cells. It is a method for men to preserve their sperm and store in a bank for future treatment. Cryopreservation is freezing of cells to subzero temperature, typically –196 o C.
Semen cryopreservation is a procedure enabling long-term, almost unlimited preservation of male reproductive cells. Cryopreservation of sperm does not reduce their quality, and therefore either a frozen or freshly collected ejaculate sample can be used successfully for artificial insemination.
Sperm cryopreservation is therefore a suitable method for any future use:
In cases of surgical sperm collection from testes or epididymides, the acquired material is frozen in order to limit any potential repetition of this invasive procedure.
Oocyte cryopreservation provides the opportunity to conserve patient's eggs or oocytes at very low temperatures for future attempts at conception using IVF. Unlike sperm cryopreservation, egg freezing has a very short history. Around 100 and 200 children have been born worldwide following egg freezing. Although these children do not appear to exhibit unusual health problems, there is not enough data to conclude that this method is safe. Therefore egg freezing is considered experimental and patients who request oocyte cryopreservation will be offered the procedure as part of a research protocol.
Egg freezing requires that the patient undergo ovarian stimulation and surgical procedures to acquire the oocytes. The oocytes are chilled by one of two methods, slow-rate cooling or ultra-rapid freezing (vitrification). Upon thawing, in vitro fertilization procedures are needed to inseminate the eggs and to culture resultant embryos. Selected embryos may then be transferred into the patient's uterus.
Oocyte cryopreservation is appropriate for women under 30 years of age who wish to defer family building into later years when ovarian output may decline, for couples who wish to limit the number of embryos created by assisted reproduction, or for women facing treatment such as cancer therapy that may diminish ovarian function.
Embryos can be cryopreserved and stored at very low temperatures to provide future opportunity for achieving conception. Embryo freezing is usually part of the in vitro fertilization and embryo transfer strategy when the number of high quality embryos exceeds the number required for immediate transfer into the uterus. Cryopreservation of human embryos has been shown to be a successful procedure and there are no reports of increased birth defects in pregnancies achieved through this process.