Egg and Ovarian tissue Cryopreservation
The first baby born from a frozen – thawed egg after fertilization in the laboratory under assisted reproduction was reported in 1986. However, despite the great importance of this scientific breakthrough, the success rate was so low that the freezing of eggs in everyday practice was prohibitive.
Since 1986, the number of births from cryopreserved eggs has been rapidly increasing thanks to the major advancements made in the field of cryobiology in combination with the IVF.
More specifically, three technological breakthroughs in assisted reproduction (microinjection, cryoprotectants and vitrification technique) have changed the data reported so far. Now, young women with cryopreserved eggs have approximately the same chances to achieve pregnancy as women who undergo conventional IVF.
Many studies have been published in recent years on the efficiency of vitrification of both eggs and embryos. More specifically, the vitrification method involves the use of cryoprotectants in high concentration and the rapid cooling rate of eggs at 20.000 °C / min.
One of the main advantages of the vitrification technique is the prevention of intracellular ice crystal formation since the cell is dehydrated before freezing.
Of utmost importance to the survival and fertilization of eggs after freezing is their pre-freezing quality. If the quality of the eggs (which is related to the age of the woman) is good, then the survival rate after thawing can reach 96%, their fertility rate 80% and the clinical pregnancy rate at 37.5% per cycle.
In other words, success rates do not differ from those in convention cycles with fresh eggs. Therefore, higher success rates are observed in women of younger age with good quality eggs while in women of older age (>40 old), success rates decrease dramatically due to the expected low quality of eggs.
It is important to provide accurate information to women who choose to freeze their eggs.
Some recommendations of the European Society of Human Reproduction and Embryology (ESHRE) worth mentioning include:
According to the latest literature, we expect a baby to be born from about 20-25 frozen eggs in women younger than 36 years old. This means that it may take more than one ovarian stimulation effort and egg collection to collect the corresponding eggs.
Women who are interested in freezing their eggs for the future should be informed that the greatest chance of having a baby is through physical conception at the youngest possible age and experts should be careful not to give too much hope about the cryopreservation. Fertility preservation should be presented as an additional option that can increase the chance of a woman having a baby, but it is not a guarantee of success.
Although ovarian cryopreservation is not recommended for women over the age of 38, it could be performed only in exceptional cases where ovarian reserve is sufficient.
The vitrification method is no longer considered experimental and, according to studies, embryos conceived from cryopreserved eggs do not show abnormalities. However, the method is considered relatively new, and more studies in children born from cryopreserved eggs are necessary to confirm the safety of the method.
When would it be best to freeze a woman’s eggs:
In the event of a tumor where women must undergo chemotherapy/radiotherapy. Cryopreservation of the eggs is essential for the future preservation of a woman’s fertility because chemotherapy/radiotherapy has a qualitative and quantitative effect on the ovarian reserves of the eggs.
In cases where the law prohibits the cryopreservation of embryos. (In Italy from 2004 to 2009, the law prohibited the fertilization of more than 3 eggs and the freezing of the most suitable eggs. The Greek legislation allows for the time being the freezing of both the eggs and the embryos).
In case a young woman wishes for several reasons to preserve her reproductive ability for the future. Social, educational and financial pressure often lead women to postpone pregnancy even until the age of 40. At this age, however, the success rates both in vivo and in vitro are lower while there is a risk of miscarriage.
Therefore, freezing a woman’s eggs at the age of 30 helps to preserve her “fertility frozen in time” until she chooses to have a child with the right partner. In recent years, the freezing of eggs for social reasons (social freezing) is becoming more and more frequent in both the USA and Europe.
The freezing of eggs is a new technique of assisted reproduction providing the opportunity to women to freeze their eggs and choose when they would like to use them.
This technique also enables women who need medical treatment, such as chemotherapy, to freeze their eggs before treatment and use them when their health permits.
In recent years, vitrification has revolutionized the field of egg cryopreservation. According to recent data, combined with the results of our clinic, we expect a survival rate of >90% while pregnancy rates resemble those in the cycle where fresh eggs are used. Egg cryopreservation is therefore an affordable option for all women.
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