In order to be stored, sperm is frozen in very cold temperatures. The sperm can be stored for many years, then thawed and used in inseminations or IVF. Freezing may reduce the ability of sperm to fertilize eggs but does not increase the risk of birth defects or chromosomal abnormalities.
The most common indication for sperm freezing is for donor sperm insemination. Sperm freezing prior to cancer treatment, which may affect future sperm production, is another indication. Freezing may also be done when the male partner may be absent (e.g. for military service); fertility treatments may therefore continue in his absence. Sperm can also be frozen prior to medical treatment such as a vasectomy.
Sperm of very poor quality or quantity does not survive the freeze-thaw process well and should not be frozen. The freezing and thawing process may decrease the number of viable sperm and the likelihood of pregnancy unless IVF and ICSI is performed.
