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Freezing eggs

While freezing sperm and also embryos during the pronuclear, 8-cell or blastocyst stage has been a standard method for many years, up until 2010 it was not known that a similar effective method is possible for freezing unfertilised eggs. In 2010, the first European working groups were able to demonstrate that similar pregnancy rates using special freezing techniques could be achieved as with using fresh eggs. In the beginning, egg freezing (cryopreservation) was mainly intended for women who as a side effect of imminent treatment would probably become infertile, e.g. in connection with chemotherapy. In the meantime, however, this technique was also being used to provide women with a more flexible solution. Thus women, who for private or work-related reasons could not or did not wish to become pregnant at that particular time, were able to freeze their eggs and use them to try to become pregnant at a later date. Such freezing of unfertilised eggs is also called “social freezing”.

Freezing unfertilised eggs: Biological background

A woman is born with a certain number of eggs, and no other eggs are produced during her lifetime. The woman’s egg reserves reduce with age. 

So as a woman gets older, it presents two problems in relation to infertility:

  1. The older a woman is, the less eggs she has in reserve to ensure successful ovulation. This reduces the chances of fertilisation taking place.
  2. The woman’s age also affects the quality of the eggs. As a rule of thumb, the likelihood of malformations, pregnancy complications and miscarriage increase from the age of 35 and the likelihood of becoming pregnant is reduced. In fact, this development begins before the age of 35, but the effect here is significantly less.

Freezing eggs can increase the chances of becoming pregnant at a later date, as healthy eggs are removed and stored as early as possible.

How are eggs frozen?

Egg freezing takes place essentially in three steps:

1. Egg retrieval

If a woman decides to have her eggs frozen, the first step is removal of as many eggs as possible. For this procedure, the woman is generally given hormones to stimulate egg maturation. Regular ultrasound scans can be done to monitor ripening of the follicles. At a suitable time and under local anaesthetic, the eggs are removed using a thin needle that is passed up through the vagina. The woman does not need to worry that her egg reserves will be reduced by removing several eggs. Each month, there are a certain number of eggs that are “receptive” to stimulation. During a natural cycle, there is a single follicle that persists, while the other eggs during this cycle are lost. During stimulation, it is these monthly eggs that would otherwise have been lost that will be used.

2. Storage

The eggs that have been removed are stored at a temperature of minus 196°C and can be safely stored in this condition for decades. The more eggs that are stored, the greater the chance of becoming pregnant. Based on the most reliable studies available to date, the chance of a successful birth with 10 stored eggs is 40%, 60% with 12 eggs and 90% with 20 eggs when these are removed at the optimal time (i.e. when the woman is less than 30 years).

3. Fertilisation

If it later transpires that pregnancy cannot be achieved naturally, the couple can use the cryopreserved egg. The egg is fertilised with sperm from the partner (or a sperm donor) outside the womb (in vitro fertilisation), and then the fertilised egg is transferred into the womb.

When is the optimal time for freezing eggs?

As the natural chances of becoming pregnant are already reduced by the time a woman reaches the age of 30, it is appropriate to freeze eggs as early as possible. Based on the most reliable studies available to date, the chance of a successful birth with 10 stored eggs is 40%, 60% with 12 eggs and 90% with 20 eggs when these are removed at the optimal time (i.e. when the woman is less than 30 years).

If the eggs are frozen after fertilisation has taken place, there is a much higher chance of survival of the eggs and subsequent pregnancy.

How many eggs will be removed?

Freezing your eggs certainly increases the likelihood of a subsequent pregnancy, but this cannot be guaranteed. To increase your chances even further, freezing and storage of several eggs is carried out. The older the woman is when she freezes her eggs, the less likely there is to be a subsequent pregnancy as the egg quality has already been reduced. Therefore, as many eggs as possible should be removed, which in this situation can be difficult as the egg reserves have already been reduced. Multiple hormone stimulations and egg retrieval procedures may therefore be necessary.

Risks and side effects for mothers and babies

According to multiple studies, there are about the same risks for babies born following pregnancies where thawed eggs were used as there are for babies born following pregnancies with normal IVF/ICSI cycles. The hormone stimulation that is required in connection with egg freezing generally only causes mild strain on your body. Thanks to suitable stimulation protocols, ovarian hyperstimulation syndrome rarely occurs nowadays. Individual counselling is provided as part of your treatment.

Further topics you might be interested in

We are here for you!

Please feel free to contact us!

Our opening times:

Mon and Thu: 08:00 - 18:00
Tue, Wed and Fri: 08:00 - 16:00
Sat, Sun and holiday: 08:30 - 15:00

Schedule an appointment:

Fill out the contact form

✉ info[at]storkklinik.dk
+45 32 57 33 16

We look forward to hearing from you!