Tissues and cells, including sperm, may be frozen and stored through a process called cryopreservation. Semen samples are prepared first with a solution that minimizes damage during the freezing and thawing processes. The samples are then placed in vials, sealed and slowly frozen in liquid nitrogen vapor. Frozen samples are stored in liquid nitrogen at a temperature of -196 degrees Celsius (-320 degrees Fahrenheit) [source: Fairfax Cryobank].
Sperm's susceptibility to damage during the freezing and thawing processes varies from donor to donor and between samples. After thawing, samples are tested. They must meet certain quality standards: Post thaw samples must contain a minimum of 20 million motile sperm per milliliter, with no less than 25 percent motility [source: American Society for Reproductive Medicine].
Previously frozen sperm doesn't live as long inside a woman's uterus as fresh sperm. Thawed sperm lives up to 24 hours while fresh sperm can live for three to five days. The risk of birth defects from conceptions with donated sperm is reportedly no different than the rate with natural conception: 2 to 4 percent [source: American Society for Reproductive Medicine].
Frozen semen seems to have no expiration date as long as the storage environment is well maintained and stable. Specimens may be stored until an individual decides to withdraw sperm for assisted reproductive treatments or the donor decides to end his storage contract. In 2005, the American Society for Reproductive Medicine (ASRM) published a report that several women had normal pregnancies and births from semen stored for 28 years [source: Xytex].