Cryopreservation is freezing of embryo and egg cells. Embryos are frozen at the blastocyst stage at the temperature of -196 °C. Cryopreservation can take place if there is a surplus of embryos, which is stored for future embryo transfers without having to repeat the stimulation. It can also be done in other cases, when a delay of embryo transfer is required because of the patient’s sickness, or when there is a risk from ovarian hyper-stimulation, thin endometrium, or when a patient undergoes radiation or chemotherapy, as to perform the PGD (preimplantation genetic diagnosis).
Embryos can be frozen for a long time, or as long as it is prescribed by law (one to ten years).
Sperm can also be frozen. Freezing does not alter the sperm quality. This method is used in the MESE and TESE procedures, for semen collected by means of electrical stimulation of the prostate (paraplegic population), in cases of upcoming orchidectomy or chemotherapy (testicular tumors), long absence of a husband (sailors, etc.).