Egg freezing / Oocyte cryopreservation: prolonging fertility

Semen cryopreservation has been commonplace in IVF centres since the mid-eighties. Thanks to the effectiveness of the technique, many men have been able to preserve their fertility in an easy and safe way.

On the other hand, oocyte cryopreservation, due to its higher complexity and lower effectiveness has not been possible until now except as an experimental technique.

In the last few years, however, with improvements in new cryopreservation techniques, especially vitrification, we have had to reconsider our way of thinking. Today we can expect a survival rate of over 80% (the majority of frozen oocytes survive when we defrost them). Thus we have moved from an experimental field to an effective technique used to preserve fertility. Frozen oocytes that survive the defrosting process behave in a similar way to fresh ones, meaning they can be fertilized by the spermatozoid and have the same chance of developing into embryos capable of being implanted and developing into healthy babies.

Today an increasing number of women are delaying pregnancy to a later date and are therefore interested in preserving their fertility.

It is well known that the effectiveness of current cancer treatments is continually improving. However, we also know that in most cases chemotherapy and radiotherapy create definitive infertility when carried out on women during their fertile years. Therefore, when diagnosed with cancer, the chances of survival are high and that makes it necessary to think about the patient’s future ability to have children. For these patients, cryopreservation is often the technique of choice.

But this is not the only case for which oocyte cryopreservation is advisable. Social and professional circumstances lead women to delay pregnancy. Moreover, fertility in women decreases with age. From the age of 35, fertility is reduced and falls sharply after the age of 40, reaching zero from the age of 45 and onwards. There are many women who reach this age range and are not yet thinking of having children in the short term. Many of them may not have a partner or perhaps their financial or job situation won’t allow them to have a child at that time.

For all these women, oocyte cryopreservation is a way of preserving a real possibility of becoming a mother later in life when the time is right for them to go ahead with a pregnancy and the care of future offspring.

Oocyte Cryopreservation in Spain Oocyte Cryopreservation in Spain

Retrieval procedure

In order to freeze oocytes, we have to follow the same steps as an In Vitro Fertilization treatment. In the last few years we have been able to simplify the steps required to retrieve oocytes.

Before the treatment begins we meet with the patient to go through all the relevant issues. We review all the information and individually assess the possibilities of success, which mainly depend on the patient’s age and the condition of her ovaries. The prognosis is better if the woman is under 35 years old, does not have endometriosis and the ovaries have not undergone prior surgery. Nevertheless, each case has to be individually assessed before a decision is made.

The procedure can generally be scheduled in just one visit and the follow-up consists of periodic scans and a blood test.

The collection technique is quite simple. It is completed with the help of a vaginal ultrasound scan. General anaesthesia is not necessary and the procedure takes less than 10 minutes. During the collection of the oocytes, a mild anaesthetic is given to the patient to avoid any kind of discomfort. Once the procedure is over, recovery time is fast so that most patients are able to leave the clinic after one or two hours.

Before the retrieval, the patient undergoes ovarian stimulation in order to obtain the right number of oocytes. During the stimulation stage, the patient is periodically monitored to assess the ovarian response. If there is any question about egg quality or quantity, the treatment is cancelled. Once the ovarian stimulation has started, the treatment takes between 7 and 10 days.

Once the oocytes have been retrieved, they are analysed by our team of embryologists. In most cases the oocytes are suitable for cryopreservation. The patient is then informed about the number of retrieved oocytes. In extreme cases, if there is any doubt about their suitability for freezing, a decision is made based on the patient’s preferences.

Once the procedure is over, the oocytes are kept in our bank at the patient’s disposal for an indefinite time (the patient must use them before she becomes 50 years old, which is the age limit for IVF in Spain). If the woman finally decides not to use her oocytes, she can donate them to another woman, donate them to scientific research or they can be destroyed.

When the woman decides to use her cryopreserved oocytes, they are defrosted. They are then fertilised using the partner’s (or donor’s) spermatozoids and the resulting embryos are then transferred to the woman’s uterus through a procedure much like a simple gynaecological check-up.

Currently we see a great number of older women with very low fertility or, in most cases, none at all, who come to our clinics looking to become pregnant. At Instituto Bernabeu, one in three IVF treatments requires the use of donor oocytes. This obviously bears significant emotional implications for the patient. In the very near future, most of these patients will be able to have their own biological children through the prior cryopreservation of their own oocytes.


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Instructions for preparing and administering GONAL: medication for stimulating oocyte growth.

Instructions for preparing and administering PUREGÓN: medication for stimulating oocyte growth.

Instructions for preparing and administering FOSTIPUR: medication for stimulating oocyte growth.

Instructions for preparing and administering OVITRELLE: medication for inducing ovulation.

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