Cryopreservation is the freezing and thawing of embryos for use in future IVF cycles. Sperm can also be frozen for men who are about to undergo surgery, chemotherapy or radiotherapy which could possibly impair their future fertility.
During an IVF cycle there may be some surplus embryos created. The advantage of cryopreservation is that you can use the embryos in future IVF cycles. In this way ovulation induction is avoided which also dramatically reduces medication cost. The success rates vary depending on patient characteristics, embryo quality and clinical history. However, success rates are lower than fresh cycles.
On the bright side, couples that are able to use frozen embryos can have children that are healthy and normal. Many studies have evaluated the children born from frozen embryos (frosties). The result has uniformly been positive with no increase in birth defects or development abnormalities.
In summary, embryo cryopreservation adds an important dimension to assisted reproduction. It extends the possibility for pregnancy when fresh cycles fail or when couples want additional children after a successful embryo transfer. Cryopreservation helps avoid many ethical dilemmas by eliminating the need to dispose of embryos for couples unwilling to donate them to other couples or to scientific investigation. It also offers an alternative to couples that might transfer too many embryos and risk a multiple gestation pregnancy.
Some men have very few sperm or perhaps produce sperm that may deteriorate over time. Other men have difficulty producing a sample on the day of treatment so banking some sperm in advance can reduce this difficulty.
Sperm is frozen in a medium (cryoprotectant) that protects them from damage during the freezing process. Consent is required to freeze sperm and it can be frozen in excess of 20 years. There is no evidence that sperm deteriorates over time in storage.