CRYOPRESERVATION

Cryopreservation is a method of freezing tissues and cells with liquid nitrogen at -196 degrees Celsius, in order to preserve them for a longer period of time. The spermatozoids are ‘quickly’ frozen using a special method for that procedure. Spermatozoids that have been preserved this way are viable for several years. When needed they can be thawed and reactivated using a specific medium for that purpose.  Unlike the spermatozoids, the embryos are much more sensitive to this freezing and thawing process so about 10-20 % of the embryos do not survive this process. Thus, we always exclusively flash freeze only embryos that are of highest quality.

The most common reasons for cryopreservation are overstimulation of the patients, when it is indicated that immediate pregnancy would not favor the patient, or when there are multiple high quality embryos. The first pregnancy after using cryopreservation was achieved in 1983 and the first newborn baby after this process was applied was in 1985. So far, there isn’t sufficient data for greater risk of malformations of the fetus, i.e. a pregnancy after cryopreservation is a pregnancy as any other because when the embryos are flash frozen, all the metabolic processes are stopped for that period of time.

The success of this procedure depends on various factors such as the patient’s age and the number of transferred embryos. The percentage of pregnancies achieved through this method is 20-50%, which is considered high percentage rate and is a testament to the resilience of human embryos.

Egg cells are the most sensitive to the process of cryopreservation, but by applying the process of vitrification, the survival rate after the thawing is 90%, the percentage rate for fertilized thawed egg cells is 75 % and the rate for implanted egg cells that have been treated this way is 20-50%.