Cryopreservation – freezing of reproductive cells and embryos
The process of freezing of reproductive cells and embryos has become an integral part of assisted reproduction methods. It is a procedure in which reproductive cells or embryos that are not used immediately for fertilization or transfer to the uterus are frozen at temperatures down to -196 °C. This allows them to be stored for a virtually unlimited time.
Cryopreservation (freezing) of embryos
In the event that more embryos are obtained within an artificial insemination cycle, we transfer only one or not more than two most optimally developing embryos to the uterus. We recommend freezing the excess embryos and keeping them for the couple for the future. The survival rate of the embryos after thawing is high, so the couple has a chance to undergo cryoembryotransfer (CET) in case of non-pregnancy after the transfer of the fresh embryo. This is only preceded by the preparation of the uterine mucosa for the reception of the transferred embryo. The woman does not have to go through the whole stimulation process followed by egg retrieval again. In the case of good quality of embryos after thawing, the chances of becoming pregnant after cryoembryotransfer are similar to those in the transfer of fresh embryos.
Sperm freezing is used in patients before cancer treatment, as well as in a sperm donation program. Sperm survival after thawing is highly individual, but generally the freezing and thawing process is survived by approximately 50% of sperms. Depending on the parameters of the semen analysis, the dose of sperm after thawing can be used either for intrauterine insemination, where the insemination dose should contain at least 15 million motile sperm. In case of suboptimal semen analysis parameters, the eggs can be fertilized using the micromanipulation IVF techniques.
Freezing of oocytes
This represents a method of freezing oocytes (eggs), which is implemented in women before cancer treatment or in women who do not plan to become pregnant at the moment and want to keep their eggs frozen for the future (the so-called social freezing). Freezing of eggs is preceded by hormonal stimulation of the ovaries taking approximately 12 days. The retrieval of mature eggs is performed under general anesthesia and the obtained eggs are immediately frozen and stored in liquid nitrogen. Cryopreservation is performed by vitrification – ultra-fast freezing of eggs in special straws.
Think about your fertility before it’s too late
Freezing of eggs (cryopreservation of oocytes) is a routine part of assisted reproduction techniques. It offers women a real chance to have their own genetic child even in higher age. The procedure comprises egg retrieval and storage while at the age when high quality of oocytes can still be assumed. This increases the chances of success if the woman decides to become pregnant at an older age as the collected eggs do not age.
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Why is it convenient to freeze eggs?
Fertility is a matter of age and this factor plays a crucial role in women. Every girl is born with a certain number of eggs in her ovaries and their number only decreases during her life as the eggs gradually cease to exist. After the age of 30, this decrease in the number of eggs may be so significant even in a healthy woman that it may endanger her fertility. It is a natural symptom of the aging process.
The problem is that as the number of eggs decreases with age, so does their quality. This is caused by errors in the maturing of the egg as well as the incorrect volume of genetic information in the egg. Already about eight years before menopause (the last menstruation in the life of every woman), the quality of the eggs gives the woman only a minimal chance of becoming pregnant and giving birth spontaneously. And already at the age of 40, the chance of a woman getting pregnant from her own eggs is relatively low. Also the success rate of assisted reproduction methods in this age group is somewhere between 15 – 17%.
We are currently witnessing a trend where women postpone their pregnancy to a higher age. Women want to be better prepared for their role of becoming mothers. It is certainly wise to start a family with a suitable partner and at the right time, however, one also needs to think about the risks of postponing pregnancy for too long. Social freezing – freezing and storing one’s own eggs for social, not medical reasons – represents some sort of “insurance policy” against the situation that when the woman decides to have a child sometimes at a later age, it won’t be too late.
When is the best time to freeze eggs?
The best time for freezing your eggs is before you reach the age of 30. However, we generally accept the age of 35 as the limit for social freezing to be meaningful and reasonable. In the group of women between the ages of 35 and 38, the freezing of eggs is associated with a lower success rate of the treatment. Therefore, we can no longer be so sure that such frozen eggs will help the woman fulfill the dream of having her own child in the future. After the age of 38, we recommend re-considering the decision to freeze eggs on individual basis. There are also health-related indications in which eggs are frozen in much younger women. This concerns premature ovarian failure, a cancer or a more severe degree of endometriosis.
For how long can eggs be frozen?
There is no strict limit in terms of how long eggs can be frozen. In Slovakia at the moment, duration of egg freezing does not have any limit in the law. The process of freezing and thawing represents the most risky processes for the egg. On the other hand, duration of storage does not significantly affect its quality. Naturally, strict storage conditions must be ensured. This is why we have applied a system of controlling the nitrogen level in our storage containers, which significantly increases the safety of egg storage.
However, if a woman has frozen eggs and wants to use them in the future, she should certainly keep in mind that pregnancy at an older age can be quite risky, and therefore she should not postpone the decision about her motherhood until the distant future. Slovak legislation does not set an upper age limit for women who may undergo infertility treatment with their own eggs. The recommended limit for the use of donor eggs is the age of 51 years. as soon as possible after the retrieval and can then be stored in special containers in liquid nitrogen for a long time.
What is the procedure for egg retrieval and freezing?
The process of egg freezing is similar to the standard in-vitro fertilization cycle. The woman undergoes hormonal stimulation, which results in maturing of several eggs in her ovaries. Once we assume that the eggs should be matured, the egg retrieval procedure is planned. As a standard, this is a procedure under general short-term anesthesia, in which follicular fluid with eggs is aspirated from the ovaries through the vagina under ultrasound guidance. Mature eggs are frozen as soon as possible after the retrieval and can then be stored in special containers in liquid nitrogen for a long time.
- initial consultation appointment,
- selection of the most appropriate stimulation protocol,
- hormonal stimulation, most commonly by subcutaneous injection for approximately 10 days,
- a follow-up assessment to determine the ovarian response to stimulation after approximately 8 days of drug administration,
- egg retrieval under short-term anesthesia,
- freezing and storage of eggs.
Why is it necessary to undergo hormonal stimulation?
In order for a woman to be able to store her frozen eggs as a kind of insurance policy for the future, it is advisable to have about 10 eggs retrieved and frozen. One should bear in mind that not every egg is genetically healthy. Moreover, not every genetically healthy egg will cope with the freezing and thawing process, and not every thawed egg will be successfully fertilized and develop optimally. In a natural female cycle, only one egg matures. Hormonal stimulation is necessary to ensure a higher number of eggs matures and no repeated retrieval needs to be performed to ensure the optimal number of stored eggs. Statistics show that the chances of a couple to bring home a healthy child developing from a single frozen egg are somewhere between 5-12%, depending on the age of the woman at which she underwent egg freezing. These are the reasons why we recommend having at least 10 eggs frozen.
What are the risks?
The medical risks involved in this procedure are really minimal. The risk of hyperstimulation syndrome, which is considered to be the most serious potential complication of assisted reproduction, is very low. Because the embryo is not transferred to the uterus, the hyperstimulation symptoms, if they appear at all, last only for a very short time. Each woman should make a well-thought decision about freezing her own eggs for future use. Of course, such decision depends on her reproductive plans – at what age she would like to become a mother, whether she currently has a partner with whom she intends to have children and many other factors.