For a long time, cryopreservation of eggs was considered to be a utopian project: its structure is too vulnerable and the risk of genetic disorders in a baby is too high if it is damaged in the process of freezing. In 1986, contrary to all pessimistic prophecies, the experiment of Australian fertility specialist Christopher Chen ended well. The next ten years, only a single mention of children born into this world appeared in scientific journals.
The slow freezing that Chen used was ineffective: only 10% of the eggs survived. Retrograde mistrust grew, but when fast freezing (vitrification) was tested for the first time in the late 1990s and efficiency increased to 90%, even skeptics threw a white flag.
And although there is not enough time to collect statistical data, this is no longer just a scientific experiment, but a promising technique implemented in practice in all developed countries.
The number of eggs measured by a woman for the entire reproductive phase of life is laid in the period of prenatal development. They are in the ovaries in an embryonic state inside the follicles – special sacs that fill with fluid as they mature.
Since new eggs do not increase during life and several thousand follicles die off every month, their supply is constantly melting.
It is hard to believe, but the biological clock starts counting down long before birth. During the period of prenatal development, about 7 million eggs are formed in the ovaries, and by the time the girl is born, 1–2 million remain. In the period of fertility, which lasts 35−40 years, ovulation are from 300 to 400 eggs.
At the age of 43–45 years, the ovaries are still working, the rhythm of menstruation is preserved, but the number of eggs by this point is already minimal. After the onset of menopause in the region of 50 years, ovulation no longer occurs, and the chances of conceiving a child naturally disappear.
With age, the eggs lose not only in quantity but also in quality. Our whole body is made up of cells. Each has a nucleus that contains a DNA molecule – the program for which it should work.
The egg has such a nucleus, only the value of the information contained in it is much more important, because it is the genetic material that will be used to create the future baby. The problem is that during life under the influence of external influences: malnutrition, poor ecology, unhealthy lifestyle, alcohol and tobacco addiction – the DNA molecule is damaged.
According to statistics, in 20 years, only one woman out of 1200 gives birth to a child with Down syndrome, and in 40 years – one out of 120.
In parallel, aging processes take place in our body, and its first signs are reproductive specialists (unlike gynecologists, who state only menopause), they notice after 35 years, and in 38-39 years they become obvious. In the cytoplasm of the egg are power stations that support its livelihoods. Scientists believe that these “plants” wear even faster than the DNA molecule.
Over time, they begin to produce less energy and protein (the building material necessary for the development of the baby), and for this reason, after 40 years, the development of the embryo often stops. The statistics confirms this assumption: according to the standard IVF program, one cycle in women under 35 years old occurs in 40% of cases, 35–38 in 35–40%, after 38 – in 25–30%, and after 43–44 – just 5%. Gynecologists explain these figures by the fact that after 35 years, women have accumulated diseases of the internal genital organs: fibroids are formed, endometriosis often begins, and adhesions form in the fallopian tubes from past infections.
Reproductive experts see the main cause of age-related infertility in the aging of the eggs themselves. And although this decision was made by nature itself, modern medicine has found a way out.
Cryopreservation of eggs gives a woman the opportunity to keep the most healthy and postpone the moment of birth of the baby for a long time.
Freezing eggs performs several important missions at once. First, this method allows you to create an egg bank that serves the same purpose as the sperm bank. In many European countries such repositories already exist, and women who decide to have a baby after 40 years of age can use it.
The main advantage is that now you don’t have to spend a lot of time looking for a donor egg. Secondly, cryopreservation is the only chance for girls and women suffering from cancer.
After a course of chemotherapy, the ovaries are severely damaged, and menopause occurs much earlier.
Having frozen the eggs before the start of treatment, such patients reserve the right to become a mother in the future (men have the opportunity to save their gene pool for a long time already). However, for women with cancer, ovarian stimulation can be carried out only with the permission of the council of oncologists.
Thirdly, it is not forbidden to resort to the vitrification method for purely pragmatic purposes. If the prince on a white horse never rode up to 35–37 years old, you can freeze the eggs, wait another quietly, and when the betrothed appears, conceive the baby using IVF. The “Fertility Preservation Program,” as doctors called it, can be used in other life situations.
For example, if there is a satellite, but it’s too early to have children, or if you want to give birth to your second child after 40.
Since only one egg matures in one cycle, and doctors recommend freezing at least 5–6 pieces, their growth should be accelerated. For these purposes, before the vitrification procedure, a woman is prescribed a 10-day course of drugs containing follicle-stimulating hormone (FSH for short), which in the body produces the pituitary gland. In preparations, the dose of FSH is higher, therefore, in one cycle, doctors can receive on average from 4 to 15 eggs.
Exactly the same training women undergo before the procedure of IVF. Statistics accumulated over 20 years shows that the use of this drug does not increase the risk of developing cancer. And although during the period of stimulation of the ovaries in patients, blood may thicken, leading to the formation of blood clots, the problem is easily solved by additional medications.
Doctors have known this side effect for a long time and have learned how to prevent it.
In the process of stimulation, the growth of follicles is monitored by ultrasound (the eggs themselves are not visible on the monitor due to their microscopic size). When they reach the desired degree of maturity, the puncture of the eggs is carried out. A woman is given a short intravenous anesthesia, a special needle is punctured the wall of the vagina and eggs are taken from the follicles.
This procedure is considered an operation, but the seams do not impose. If, for various reasons, only one follicle matures, puncture can be performed without anesthesia.
Purely theoretically, stimulation with hormonal drugs can be avoided and only the egg cell that matures in the ovary in a natural way can be extracted. But since the task is to create a reserve, and not the last hope, puncture in this case will have to be done several times. The operation itself is considered harmless, but you will have to pay in full for each manipulation.
One puncture costs about 60,000 rubles, the course of stimulation with FSH drugs is about 40,000.
The oocytes extracted from the ovaries are transferred to a special nutrient medium, then treated with a special solution that ensures even freezing, and immersed in liquid nitrogen. The vitrification method allows for 1 second to cool the eggs to minus 100 ° C.
The old technology was dangerous due to the fact that in the process of slow freezing (in 1 second cooling took place only 1 degree) ice crystals were formed inside the egg, traumatic for the DNA molecule.
The shelf life of frozen eggs reaches 10 years. At least, this is exactly the number that the doctors give to the patients. Most likely, the egg can be stored longer, just for long predictions is not enough statistical data.
For comparison: in the medical press there are reports of children born as a result of fertilization of frozen embryos that have lain in liquid nitrogen for 15 years.
At the right time, the egg can only be defrosted and washed from the protective solution. Fertilization is performed by the method of IVF on the same day.