Sperm cryopreservation is performed with the use of cryoprotectants which aim to protect the various cell structures of the sperm from the drastic change in temperature.
The cryopreserved samples are kept in liquid nitrogen at -196 °C and can be maintained indefinitely in this temperature. The sample is placed in ampoules labelled with a name, a specific code and the respective freezing date.
The sample is placed in a specific position in the nitrogen containers while the unique ID of each sample is maintained in a file in the laboratory which can only be accessed by the embryologist. During the thawing phase, the sample experiences a partial loss of spermatozoa motility as high as 40%. Samples with a small number of spermatozoa or limited motility are usually unsuitable for cryopreservation, since the sample will be unsuitable for fertilization after thawing.
The freezing of sperm is proposed in the following cases:
Subject to the provisions of the law, the cryopreserved sample is stored for 5 years in the case it was provided by the male partner himself and for 10 years in the case it was provided by a donor.