Sperm cryopreservation is the process used for the long term storage of sperm cells. This process freezes the sperm cells in a controlled manner using liquid nitrogen to reach temperatures around -196 degrees Celsius. The process is much more involved than simply placing a sperm sample in a freezer.

How do the sperm not become damaged during the freezing process

Sugars and the specialized chemicals DMSO, and glycerol are added to the sperm specimen to prevent damage to the cells during the freezing process. Some of the sperm cells will inevitably become damaged during the freezing process, but the additives and controlled freezing helps to minimize damage and so many of the sperm cells remain viable after freezing and thawing.

Does the freezing process pose risk of birth defects

There has been no evidence to show that there is any risk of birth defects that are caused from sperm that has gone through the cryogenic freezing and thawing process. Although some sperm cells from the specimen may become damaged during the process, the specimen is carefully examined and only the healthiest and most viable sperm cells will be used for the IVF procedure. All of that equates to a simple no, there is no risk of birth defects from using sperm that had been cryogenically frozen.

How long can my sperm remain frozen and still be viable

Sperm specimens that have been properly cryogenically preserved can theoretically remain frozen indefinitely. Of course this has not been put to the test because most specimens are used within a decade of being frozen. To date the oldest specimen that has been successfully used was about twelve years old.

There are several factors involved to determine how well a sperm specimen handles cryogenic preservation. If the process was executed perfectly and there have been no disturbances to the specimen during its time frozen, then it is assumed that the specimen will remain viable forever.