Vitrification or "freezing" of oocytes is an assisted reproduction technique that consists of obtaining the woman's eggs and preserving them at very low temperatures (-196°C) for an indefinite period of time.
This method is used to preserve female fertility for medical reasons or in women who want to delay the moment of motherhood. However, egg vitrification is also used in in vitro fertilization (IVF) treatments that require oocyte cryopreservation.
The main advantage of egg vitrification is that the oocyte quality is maintained for as long as the oocytes remain vitrified. This means that the eggs will have the same quality they had at the time of vitrification when the woman decides to use them.
Provided below is an index with the 11 points we are going to expand on in this article.
What is vitrification of eggs?
Egg vitrification is a procedure that consists of using cryoprotective agents and liquid nitrogen to "freeze" the eggs previously extracted from the woman's ovaries. In this way, the eggs can be preserved at a very low temperature, namely -196°C.
The technique used today to cryopreserve eggs is vitrification. Nowadays you may hear talk of egg or oocyte freezing, but the correct term is vitrification.
Indications for egg vitrification
The technique of oocyte vitrification is used in assisted reproduction centers for two main indications, which are mentioned below.
Preserving female fertility
In the case of female fertility preservation, it can be performed for medical reasons (if the patient is going to undergo, for example, an oncological treatment that will affect her fertility) or simply because the woman wishes to postpone motherhood.
If you are considering preserving your fertility to have a baby in the future, we recommend that you start by getting a Fertility Report. In 3 simple steps, it will show you a list of clinics that fit your preferences and meet our strict quality criteria. Moreover, you will receive a report via email with useful tips to visit a fertility clinic for the first time.
Delaying childbearing until older age leads to a reduction in the number and quality of eggs in a woman's ovarian reserve. This is why women may have difficulty in achieving pregnancy or a greater risk of miscarriage as they get older. Hence the importance of vitrifying the eggs when the woman is still young for later use.
In an interview with us, Dr. Sergio Rogel, OB / GYN sepecialising in fertility, told us about why fertility preservation is recommended for women:
The most important factor which we see today in assisted reproduction clinics, that produces a failure to get pregnant, is age. Basically, bearing in mind our current society, with women styding more and taking longer to find their desired job and economic stability, it becomes more interesting and desirable that women preserve some of their eggs so they can use them at a later date to become pregnant without difficulty.
Optimizing IVF cycles
Egg vitrification allows better planning of IVF cycles. This technique offers the possibility of accumulating oocytes in low responders (vitrifying the eggs obtained after several ovarian stimulations). In addition, oocyte vitrification would also allow the use of cryopreserved donor eggs without having to synchronize the donor with the egg recipient.
Egg vitrification process
Oocyte vitrification is an ultra-rapid freezing technique that employs high cooling rates and uses cryoprotective substances to protect the eggs from being damaged in the process.
Cryoprotectants are molecules that reduce the aqueous content inside the oocytes and thus protect them from the effects of low temperatures by preventing the formation of ice crystals.
In general, the oocyte vitrification treatment is divided into two distinct steps: one that depends on the gynecologists and another that depends on the embryologists of the laboratory.
The first step before starting a treatment to vitrify the eggs is to perform a vaginal ultrasound and a hormonal analysis on the woman. These tests will allow the specialist to assess the state of the patient's ovarian reserve.
Subsequently, the woman has to undergo a process of controlled ovarian stimulation, just as if she were to undergo IVF treatment. For this purpose, the gynecologist will indicate to the patient the hormonal medication to be injected so that the ovaries develop several follicles at the same time.
During this process, the woman has to visit the clinic every 2 or 3 days for check-ups to see if the follicular growth is adequate. Depending on the ovarian response, the gynecologist may adjust the dose of hormonal medication and the days of treatment.
Finally, when most of the follicles have reached a size of 16 to 18 mm, the gynecologist will schedule the follicular puncture to obtain the eggs.
Follicular puncture is a simple procedure in which, using an ultrasound-guided needle, the gynecologist aspirates the follicles to extract the eggs from inside them. The process takes about 30 minutes and the woman is sedated to avoid discomfort.
After the oocytes are retrieved in the operating room, they are taken to the IVF laboratory. There, the embryologist evaluates their state of maturation and quality before proceeding to vitrification. To do this, the eggs must first be decumulated, i.e., the granulosa cells surrounding them must be removed.
Once this is done, the most common method for vitrifying oocytes is the Kitazato Cryotop. It is a support consisting of a plastic handle to which a transparent strip is attached. After being treated with cryoprotective substances, the ovum will be adhered to this small strip.
In summary, the main steps of the oocyte vitrification technique are:
- Oocytes are dehydrated by passing them from one medium to another with increasing concentration of cryoprotectants.
- Between 2 and 4 eggs are placed on top of the support system (Cryotop) for vitrification.
- The excess medium is carefully aspirated using a pipette onto the Cryotop, so that there is as little volume as possible.
- Quickly, the Cryotop with the eggs is introduced into a vat with liquid nitrogen.
- The lid of the Cryotop is placed carefully so that the area where the oocytes are located does not come out of the liquid nitrogen.
- The Cryotop is stored in a liquid nitrogen tank for long-term preservation of the eggs.
The technique of vitrification of oocytes requires great skill and dexterity on the part of the embryologist, since these are very delicate cells.
Devitrification and use of oocytes
When vitrified eggs are to be used, the embryologist must follow a devitrification protocol consisting of the following steps:
- The Cryotop is removed from the liquid nitrogen tank into a basin also containing liquid nitrogen.
- The lid of the Cryotop is removed and the end where the eggs are located is immersed in a medium at 37°C. In this medium, the eggs will detach from the Cryotop.
- Finally, the eggs are transferred from one devitrification medium to another with a decreasing concentration of cryoprotectants to rehydrate them.
The eggs must be devitrified at least 2 hours before fertilization in the laboratory. During this time, the oocytes remain in an incubator with the appropriate culture medium and conditions.
The embryos obtained will be kept in culture for 3 to 5 days and then the highest quality embryo or embryos will be transferred to the woman's uterus in an attempt to achieve pregnancy.
Embryos that are not transferred can be re-vitrified for future use. If you want to know more about this technique, you can continue reading here: What is embryo vitrification - When and how is it done?
Advantages for egg vitrification
As we have already mentioned, a woman's ovarian reserve decreases with age. As a result, women who postpone childbearing are forced, in many cases, to resort to oocyte donation treatments.
Egg vitrification, on the other hand, offers many advantages in this regard. This technique allows women who decide to become mothers at an advanced age to have children with their own eggs.
In addition, there are other advantages of oocyte vitrification:
- Preservation of female fertility
- oocyte vitrification is extremely valuable for women who are about to undergo cancer treatment or any type of surgery that may affect their ovaries and therefore their fertility.
- Increased probability of success
- once the woman decides to use the vitrified eggs, they will be the same age as the woman was at the time she decided to vitrify them, i.e., they will be younger eggs. This offers a higher pregnancy rate, as well as a lower probability of obtaining embryos with chromosomal abnormalities that could result in miscarriage or the birth of a sick baby.
- Simple treatment
- although certain complications such as ovarian hyperstimulation syndrome (OHSS) or other bothersome symptoms of the medication may arise, in general, it is a simple and quick procedure that can be of great help in the future.
- Allows the accumulation of eggs
- this procedure consists of performing several ovarian stimulations and follicular punctures and vitrifying the oocytes obtained until an adequate number of eggs are obtained for fertilization. This process is very useful for women with low ovarian reserve and/or low responders.
Finally, there are some couples who, because of their beliefs, prefer to cryopreserve oocytes rather than embryos.
Regarding the period of time that the vitrified eggs can remain in vitrification, Rocío Díaz comments the following:
Considering that they are at cryogenic temperatures in liquid nitrogen, that they are at -196ºC and have all their biological functions suspended, the time they can be maintained is long, but still undetermined by science.
The cost of egg vitrification, though similar, varies from country to country, as one shall see in the following sections:
Cost in the USA
In the United States, the process can be divided into two phases. First, the egg retrieval procedure, which can cost anywhere between $600 to $1,500. Second, the storage fees, which cost is $1,200 per year. At some fertility clinics, it is free for the first year.
If you are considering freezing your oocytes to have a baby in the future, we recommend that you get your Fertility Report now. In 3 simple steps, it will show you a list of clinics that fit your preferences and meet our strict quality criteria. Moreover, you will receive a report via email with useful tips to visit a fertility clinic for the first time.
Cost in the UK
As regards the freezing eggs in the UK, it might be NHS funded depending on the cause and where you live.
The following is the average cost of an egg freezing cycle according to the Human Fertilisation & Embryology Authority (HFEA):
- Egg collection and freezing: £3,350
- Medication: £500-1,500
- Storage fees per year (up to 10 years): £125-350/year
- Thaw cycle and embryo transfer: £2,500
- TOTAL COST: £7,000-8,000
According to the HFEA, if you have a medical condition or need treatment for a medical condition that will affect your fertility, NHS funding may be available.
On the contrary, if you are worried about your fertility declining but have no medical condition, then it is called elective egg freezing and NHS funding is not available for these cases.
Cost in Canada
In Canada, the initial egg collection procedure typically costs between $6,000 and $8,000 CAD. To this, we should add the cost of hormones and medications, which can range from $3,000 to $6,000 CAD on average.
The annual storage fee is $350 CAD approximately.
FAQs from users
Does egg vitrification have any effect on the baby?
With respect to children or pregnancies, there is no scientific article, no serious study that tells us that there are differences between newborns born from eggs from fresh cycles or from eggs from vitrified cycles. There are many studies on epigenetics, but these studies also have to take into account other things, such as, for example, what type of culture medium was used, what type of fertilization technique was used.... But as of today there is nothing with sufficient scientific evidence to tell us that there can be any problem in the children if they have been generated with vitrified eggs.
Is there an age limit on egg freezing?
In principle, there is no age limit on egg freezing; a woman can decide to do it whenever she wants. However, one should consider preserving her fertility at a young age, as egg quality is better at this point. This, at the same time, translates into higher chances of getting pregnant in the future by means of IVF.
Which is better? Egg freezing or egg vitrification?
Without a doubt, vitrification. This technique is the one that has really made it possible to offer the technique of female preservation with all the guarantees.
First of all it would be necessary to distinguish the two techniques and their history, as well as why the conventional freezing technique was relatively valid for embryos but not for oocytes.
With the conventional freezing technique, cryoprotectants are used in low concentration for a relatively long time and a slow progressive cooling. This sometimes results in the formation of crystals that are lethal to the cells. The larger the cell, the greater the possibility of crystals forming, and if we take into account that the egg is the largest cell in the human body, this explains why this technique has produced very poor results with eggs.
The vitrification technique consists of exposing embryos and oocytes to high concentrations of cryoprotectant in a relatively short time and ultra-fast cooling (in the order of 20,000 ºC/min). As a result of this process a vitreous mass is formed (hence the name vitrification) avoiding the formation of crystals that would damage the cell.
Therefore, vitrification of eggs is undoubtedly better than freezing. It is this technique that has really made it possible to offer the technique of female preservation in a standardized way with all the guarantees.
What are the risks and side effects of egg vitrification?
Egg cryopreservation consists of three phases. First, stimulation of the ovaries is carried out to develop multiple oocytes. Here, an increase in the size of the ovaries occurs, which could lead to ovarian torsion. In addition, this phase also has the potential risk of causing ovarian hyperstimulation in the woman.
Secondly, the ovaries would be punctured in order to retrieve the oocytes. This is a simple surgical procedure that is performed under anesthesia, so complications may arise from the anesthesia itself. Bleeding may also occur.
Finally, vitrification of the eggs takes place. When these eggs are to be used, they will have to be thawed, which may pose a danger to their survival.
How much does egg freezing cost?
The average price of egg vitrification is usually between $10,000 and $18,000. However, it still depends on each fertility center. It should also be taken into account that hormonal medication for ovarian stimulation is not included in this budget and can cost between 500 and $1,000. Finally, after the first or second year of freezing, fertility clincis usually require that a maintenance fee of around $ 5-600 per year be paid for the frozen eggs.
Which is better, egg or embryo vitrification?
The truth is, there is no treatment better than other, since in both cases the survival rate after the thaw procedure is above 90% and the quality of both eggs and embryos is usually the same.
The decision between one option or the other depends on your personal decision and the advice of your doctor. If you are single at the moment of vitrification, you might wish to opt for egg vitrification only.
When is egg freezing recommeded?
The main reason for egg vitrification is to postpone motherhood. However, there are other very important indications, such as preserving fertility in the following cases:
- Women who are going to undergo aggressive treatment such as chemotherapy so that they can become mothers once they have overcome the disease.
- Women who have received or will receive some type of surgery on the ovaries, as in the case of endometriosis for example.
- Women who are going to have their ovaries removed due to a tumour.
Is egg vitrification useful in women with endometriosis?
Yes, endometriosis is a progressive disease, so vitrifying eggs to preserve them in the early stages of the disease is useful in these patients. In this way, the woman will be able to try to achieve pregnancy with her own eggs even though the severity of the disease has advanced.
Does egg freezing hurt?
In order to freeze the eggs, women need to go through a process of ovarian stimulation and follicular puncture. These procedures can be uncomfortable because they must take hormonal medication and then undergo surgery to remove the eggs. However, unless there are any complications, it is not painful.
Do vitrified eggs lose quality?
Vitrified egg cells do not necessarily lose their quality. However, it is different if the quality of the oocyte before vitrification is not the best. If the oocyte is not of good quality, the freezing and thawing process can obviously damage it.
If they are good quality oocytes, there is no reason why there should be any kind of problem. It depends more on the quality of the egg before being frozen than on the freezing technique itself.
Throughout this post, we have explained what is the egg vitrification process about from a technical perspective. If you want to learn more about fertility preservation, click here: Fertility Preservation – Cost & Options for Retaining Your Fertility.
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Glujovsky D, Riestra B, Sueldo C, Fiszbajn G, Repping S, Nodar F, Papier S, Ciapponi A. Vitrification versus slow freezing for women undergoing oocyte cryopreservation. Cochrane Database of Systematic Review 2014, Issue 9. Art. No.: CD010047.
Human Fertilisation & Embryology Authority (HFEA) (2018). Should I freeze my eggs? A guide to the latest information and statistics on egg freezing in the UK. See
Reproducción Asistida ORG. Video: ¿Durante cuánto tiempo pueden mantenerse los óvulos criopreservados? (How long can frozen eggs be stored?), by Rocío Díaz, BSc, MSc, Oct 25, 2016. [See original video in Spanish].
Sociedad Española de Fertilidad (SEF) (febrero de 2012). “Saber más sobre fertilidad y reproducción asistida”. En colaboración con el Ministerio de Sanidad, Política Social e Igualdad del Gobierno de España y el Plan de Calidad para el Sistema Nacional de Salud.
FAQs from users: 'Does egg vitrification have any effect on the baby?', 'Is there an age limit on egg freezing?', 'Which is better? Egg freezing or egg vitrification?', 'What are the risks and side effects of egg vitrification?', 'How much does egg freezing cost?', 'Which is better, egg or embryo vitrification?', 'When is egg freezing recommeded?', 'Is egg vitrification useful in women with endometriosis?', 'Does egg freezing hurt?' and 'Do vitrified eggs lose quality?'.
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