Elias Gatos, M.D.
Surgeon Gynecologist – Obstetrician
Scientific Director emBIO Assisted Reproduction Unit


Egg and Embryo Cryopreservation (Vitrification)

Developments in medicine and biology in assisted reproduction combined with the implementation of new IVF techniques provide effective solutions to a number of infertility problems of our times. One of the most innovative methods currently applied is egg and embryo cryopreservation also referred to as Vitrification.

What it is

This is a rather simple freezing method not requiring a special or complex mechanism. Human eggs have a high concentration of water and, therefore, they are very sensitive to freezing processes. Standard freezing methods have not always been successful since they allow the formation of crystals inside cells, inducing certain embryonic damage and irreversible egg damage. Ongoing research and the development of this method, have now led to the most integral vitrification system, the implementation of which achieves freezing eggs and embryos at the highest survival rates amounting to 90%.

The procedure at a glance

The vitrification procedure initially includes placing eggs and embryos in a small amount of proper high-concentration anti-freezing agent (DMSO and ethylene glycol) for a short period and then freezing them at a high pace. The high freezing rate significantly reduces crystal formation. The water inside the cells automatically freezes and there is no time to form crystals, which might lead to irreversible damage in eggs and embryos. At the standard freezing process, the freezing rate for eggs and embryos is approximately 0.3°C a minute, whereas at the vitrification method, this rate exceeds 20,000 °C a minute (70,000 times faster). At this rate and at the proper concentration of the anti-freezing solution no crystals can be formed. Post-vitrification, eggs and embryos are kept in liquid nitrogen containers until they are defrosted to be used.

Moreover, vitrification also provides total safety for these sensitive cells against viruses and diseases, whereas it also ensures their viability until they are defrosted. The toxicity of the anti-freezing solution used, as well as the required expertise may be the sole factors limiting this method.

When to apply this

This innovative method enables women and couples in general to preserve their fertility given that a successful pregnancy is directly associated with the woman’s age and the quality of eggs produced. The vitrification method is one more option for cryopreserving eggs and embryos for future use. Therefore, it allows us to create an egg bank making the egg donation programme significantly easier. This method also gives hope to a number of women of child-bearing potential and, particularly, those who:

  • Wish to delay pregnancy because of their career or education without losing their fertility.
  • Wish to delay pregnancy until they find a proper partner.
  • Have a form of cancer and wish to preserve their healthy eggs before they undergo radiotherapy or chemotherapy
  • Wish to freeze embryos left from an IVF cycle to ensure a future successful pregnancy.

Sperm cryopreservation

Some cases require sperm freezing. In these cases, sperm freezing takes place using a proper solution (cryoprotectant) protecting spermatozoa during freezing. The frozen sample may be preserved for a number of years and be used in future IVF attempts. There have been pregnancies using 15-year old frozen sperm.

Sperm freezing is performed in men having oligospermia or different sperm parameters over time or difficulties in producing sperm, in cases where testicular biopsy has been performed (spermatozoa found during the biopsy are preserved and used at a future IVF attempt), in men who are to undergo chemotherapy or radiotherapy.


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