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Cryopreservation is an extremely useful assisted reproduction technique because it allows the viability of cells to be preserved for a long time – theoretically indefinitely – in liquid nitrogen and a temperature of -196°C, with the aim of using them in the future, essentially freezing time.

In humans, this method was initially applied for the cryopreservation of sperm – the first use of cryopreserved human sperm to achieve pregnancy was in 1953 – with very good results.

The birth in 1983 of the first children from embryo cryopreservation, thawing and embryo transfer, was a significant development in in vitro fertilization because it allowed a reduction in the number of embryos transferred to the uterus and the storage of excess ones for future use.

Cryopreserved embryos can be transferred to the uterus in case of failure of the IVF attempt or in case of success, when there is a desire for a new pregnancy later.

Also, in cases of risk of ovarian hyperstimulation syndrome, cryopreservation of all embryos is performed and embryo transfer in a subsequent cycle, so, according to recent studies, the results of achieving pregnancy are equally good, and probably higher, without risk to the woman.

The same can be done in cases where the development of the endometrium is not good or the development of the cycle is not ideal.

Until recently, cryopreservation of eggs with classical methods did not have good results. However, the new ultra-rapid freezing technique, vitrification, has yielded excellent results in the survival of eggs and embryos after thawing, which reaches 90%, as well as in pregnancy rates.

This development has made it possible to cryopreserve eggs to preserve fertility.

One such case is women who have been diagnosed with cancer and, before undergoing chemotherapy and/or radiotherapy, can cryopreserve their eggs, so that they can use them after their recovery in order to have children. After all, this has been done for years in similar cases of men, with the cryopreservation of their sperm.

Another important application of cryopreservation is the ability it gives to women who are not ready to have a family, to preserve their eggs, so that they can use them for childbearing later. Studies have shown that the most important factor affecting a woman’s fertility is her age.

The ideal reproductive age of a woman is from 20 to 30 years, since then a progressive decrease in fertility begins due to a decrease in the number and quality of eggs. However, as is known, in our country, the age of having the first child for women has been postponed by 10 to 15 years and on average has reached the age of 35, with negative effects on their fertility.

Therefore, egg cryopreservation, together with contraceptives, promotes women’s reproductive autonomy: the first by giving them the opportunity to postpone their childbearing age without negative consequences and, the second, by allowing them to plan the time of having a child.

In conclusion, embryo cryopreservation is an essential part of in vitro fertilization, since it increases the effectiveness and safety of the method, while egg cryopreservation gives women the opportunity to preserve their fertility for medical or socio-cultural reasons.

Vassilis Tarlatzis, MD, PhD, FRCOG (hon) Professor of Obstetrics – Gynecology and Human Reproduction, Aristotle University of Thessaloniki, President of the Scientific Council FIVI Medically Assisted Reproduction Unit, Inter-Balkan Medical University of Thessaloniki President-elect of the European College of Obstetrics – Gynecology EBCOG