Frozen sperm prepared well and stored under the proper conditions have the potential to last indefinitely until thawing, at which point they have a viability window of approximately 24 hours. Men can store sperm for a variety of reasons and the costs for storage vary, depending on the facility. It is also possible to freeze eggs and embryos, although they tend to be more fragile than sperm and are more subject to failure in the freezer.
Before a doctor can freeze sperm, the patient usually needs some tests to check for conditions like syphilis and human immunodeficiency virus (HIV), particularly if the sperm is going to a sperm bank for use in a donor program. If the patient has a clean bill of health, he can submit a sperm sample. A technician checks the sample for motility and other characteristics to determine if it is viable. If it is not or it is borderline, the technician may recommend against freezing because the sperm may not survive the freezing and thawing process.
Preparation of sperm for freezing is important. Different techniques are in use in various facilities. One of the best is a process called vitrification, which relies on very rapid freezing to prepare frozen sperm. This can reduce the risk of damage to the sperm, and also removes the plasma associated with the sperm, which can cut down on the risk of disease transmission. Studies on the freezing process do not suggest it causes any genetic damage, and children resulting from frozen sperm are not at increased risk of genetic disorders.
Proper storage conditions for frozen sperm are critical. Cryopreservation facilities use racks and drawers to control samples in storage, both to make sure samples are not mixed up and to maintain appropriate spacing and placement to create optimal freezing conditions. If sperm are stored in a haphazard way, they may be prone to damage. The facility also maintains very stable temperatures to keep the sperm frozen. Alarm systems alert technicians when temperatures fall outside safe ranges.
Frozen sperm can be carefully thawed in controlled conditions and used in assisted fertility procedures. Thawed sperm does not live as long as fresh sperm and must be used within approximately 24 hours to be viable. Frozen sperm may be stored in batches so that if something goes wrong, another sample will be available for use. As long as the conditions are sound and the sperm was well prepared at the time of freezing, it could be usable decades later.