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Cryopreservation

Storing cells and tissue with cryopreservation

Cryopreservation is a special process that makes it possible to store cells and tissue for a long time for use at a later date. Cells and tissue are frozen and stored at minus 196 degrees Celsius in liquid nitrogen. The word ‘cryopreservation’ comes from the ancient Greek word “kryos”, meaning “cold”.

What can be stored using cryopreservation?

Cryopreservation is a method that is commonly used for fertility treatment:

  • Unfertilised eggs

When freezing unfertilised eggs, there is still quite a high risk that the eggs can be damaged during cryopreservation. This is because unfertilised eggs have a large water content (compared to fertilised eggs), which makes them more sensitive to the freezing process. Therefore damage can occur because of water crystals that are formed during the freezing process. Nevertheless, frozen unfertilised eggs should be seen as a valuable egg depot for use in future fertility treatment.

  • Fertilised eggs in the 4–8-cell stage as well as blastocysts

Using special cryopreservation processes where the cells are treated with a membrane-protective medium (cryoprotectant), the cells are brought to a stage that ensures that they can be stored for long periods of time (several years) without affecting their viability and then can be thawed when needed.</article>

When is cryopreservation appropriate?

1. In connection with artificial or assisted fertilisation

It is often appropriate to freeze fertilised eggs. If required, these eggs can be cultivated and implanted, e.g. if the parents would like another child. This process is also called frozen embryo replacement. The advantage of cryopreservation is that the woman does not have to have further hormone stimulation and egg retrieval.

2. Freezing eggs

Many young women who would like to have a child, but, for personal reasons, cannot or do not want to become pregnant during the current phase of their lives can use cryopreservation. Young women may want to focus on their careers or may have not found the right partner. In Denmark, these women can freeze their eggs for use at a later date.

How is frozen embryo replacement carried out?

When a women or a couple want to use a frozen fertilised egg to achieve a pregnancy, the egg can be cultivated and transferred to the womb. We are talking here about frozen embryo replacement. Unfertilised eggs that have been frozen are first fertilised—always using intracytoplasmic-sperm injection. 

With optimal cycle conditions, frozen embryo replacement can be done without the need for hormone stimulation. Another option is to support the development of the lining of the womb (the endometrium) with oestrogens and facilitate optimal conditions for implantation of the egg. The doctor can assess the thickness of the endometrium on ultrasound. If it is thick enough, hormone treatment with progesterone is given. Then the endometrial structure changes, and it is ready to receive the fertilised egg. A third option is hormone stimulation with the hormone FSH to support the ripening of the follicle prior to embryo transfer. Then the doctor can transfer the embryo/embryos to the womb with a soft catheter. 

What are the potential risks of cryopreservation?

Cryopreservation has been used for many years, and most studies show no negative consequences. Individual counselling always forms 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!