Sperm can be cryopreserved with a special process and using appropriate materials and it can be kept in containers containing liquid nitrogen at -196oC. Sperm can remain in this state without losing its vitality for a long time. In this way the sperm can be defrosted after the day it was taken and be used for fertilization.
This is usually done when:
- it is impossible to take sperm on the day of egg retrieval,
- there is need to preserve fertility before, for example chemotherapy.
The man must abstain from all sexual activity two to five days before the procedure. With sperm cryopreservation testing for AIDS and hepatitis B and C is needed as well.