Although cryopreservation of embryos is the most common method of maintaining fertility, nowadays egg freezing is the most applicable option for women of reproductive age who need to postpone motherhood for various reasons. Freezing difficulties due to the characteristic structure of the ovum cost more than 20 years to develop the methods before the technique reached clinically significant levels of success. Three main achievements contributed to the success: the development of the ICSI method, the improvement of cryoprotectants and the introduction of the vitrification method.
This opened a new era in the cryopreservation of reproductive material. Oocyte freezing is expected to become a leading method in maintaining fertility, and also to be used routinely in IVF in a number of cases, such as ovarian hyperstimulation, poor ovarian response, genetic mutations, donation, and more.
The egg is larger than any other cell in the human body, about 100 microns in diameter, about the size of a human hair. This means that theoretically we can see the egg with the naked eye. Also, eggs are about 4 times larger than epithelial cells and about 20 times larger than sperm. The egg contains genetic material, 96% water and energy substances. The fact is that the eggs need a lot of energy, especially after they are fertilized. Human eggs contain large amounts of mitochondria, which provide energy to cells by converting oxygen and nutrients into chemical energy. Their concentration is so high that this single cell supplies energy to the formation of an entire embryo and the birth of life during the first 7 days of zygote division. Maintaining the uniform integrity of each component of the ovum is essential for success in freezing.
How are the egss freezed?
In order to obtain the optimal number of eggs for freezing, the patient must undergo hormonal stimulation similar to that of an in vitro fertilization procedure. During this process, follicle growth is monitored, hormone levels are monitored, hormonal medications are prescribed to stimulate the ovaries, and a puncture is made to remove the eggs. After aspiration, the eggs are processed and placed in special cryoprotective media that protect the eggs from freezing. They aim to extract or convert the water content of the cell into a gel – this is an important condition for the survival of eggs after freezing. The egg passes through a series of such solutions and when the water content in it decreases, it is placed in special containers (Dewar vessels), where it is stored in liquid nitrogen (at -196 ° C). After thawing, fertilizable eggs are about 70-80%.
When is it recommended to freeze your eggs?
- In women who plan to postpone pregnancy and childbirth to a later stage. The recommended age for freezing is up to 35 years, when ovarian function is active, there is a significant ovarian reserve, and the ovaries respond well to stimulation. By this age, eggs are less likely to carry a genetic abnormality;
- In order to preserve a woman’s fertility after chemotherapy or radiation therapy for cancer;
- In women in whom the ovaries decrese their function prematurely at an earlier age;
- In women with a family history of premature menopause.