Semen freezing is a widespread procedure used to preserve male fertility. Once the sperm is analyzed, the sample is frozen. These samples are storaged in a semen bank, where they can be kept for unlimited time until its use is required.
Sperm quality is barely altered by the freezing, therefore it can be used in assisted reproductive procedures to get pregnant.
Semen freezing in based on blending the semen sample with a cryoprotectant, which is composed of egg yolk proteins, and slowly freezing the resultant mixture, lowering the temperature progressively until it is submerged in liquid nitrogen.
Freezing can be done in cryotubes, i.e. small rehearsal tubes with a capacity of 1 ml where the blend of the semen and the cryoprotectant rests, and in the first instance a slow freezing by means of vapors of nitrogen is done. Afterwards, a second freezing with liquid nitrogen is done and the cryotubes are storaged in sticks that string them.
The sperm is frozen in small pills when the semen is valuable, as in cases of HIV seminal lavage, or in a patient that freezes his semen before undertaking a chimiotherapy treatment, making its rationalisation easier in case his semen is required for several cycles of in vitro fertilisation. In such cases, the semen is kept in properly labeled receptacles that are submerged in tanks of liquid nitrogen.
Men that suffer from cancer and are set to be treated with chemotherapy and radiotherapy must preserve their fertility before undertaking these treatments, in case their wish is to be a father. Once they have overcome the disease, sperm production might be altered, or its quality decreased. After a while, there is a chance the sperm alteration could be reverted, but in most cases these drugs produce permanent male infertility.
Some patients decide to have a vasectomy as a contraceptive measure because they don’t want to have more children, but choose to save a cryopreserved semen sample as a precaution. Therefore, they still have the opportunity to become parents, either with the same partner or with a different one.
Some men experience difficulties when trying to ejaculate, and sometimes the issues come from tight schedule. Thus, if there is a preserved sample in the semen bank of the fertilisation clinic, the donor doesn’t need to be physically there when the woman starts the fertilisation treatment.
Spanish legislation compels the clinics to conduct a series of tests to determine the semen is not contamined. These tests must be carried out months after the donation is done, being thereby necessary to freeze all the collected samples.
When to use the frozen sperm
When required, the frozen sperm may be used for an artificial insemination or an in vitro fertilisation, according to the specific case. If the freezing is slow, the defreezing is fast and, in a few minutes, temperature rises from -196ºC to 37ºC. The process is 15 minutes long. From that moment on, the sperm can be processed and finally ready to be chosen in an assisted reproductive procedure.