Questions? CallMessage us


Cryopreservation for fertilisation

Freezing tissue is called cryopreservation. Cryopreservation is a special process that allows cells and tissues to be stored for a long time for later use. Cells and tissues are frozen and stored at minus 196 degrees Celsius in liquid nitrogen. The name for this technique comes from the ancient Greek word "cryos", meaning "cold".


Freezing can be used for sperm, unfertilised eggs, fertilised eggs and ovarian/testicular tissues.  


It is possible to have sperm from a male partner frozen at the clinic. We recommend this in case of prolonged absence of the partner, illness or inability of the man to give a sperm sample on command (psychological impotence).  

Donor sperm  

All donor sperm is frozen when we receive it at the clinic. This is due in part to a legal quarantine of donor sperm before it can be used.  

Fertilised eggs 

We recommend freezing excess fertilised eggs after ICSI/IVF. The procedure for freezing and thawing is now so good that virtually all eggs survive. A Danish study from 2020 (Stormlund et al: and our own results show that the chance of pregnancy is as good when using frozen eggs as when using fresh eggs. The advantage of freezing is that the woman does not need to have a new hormone treatment and egg retrieval for another attempt. Frozen egg storage can be done in a woman's own cycle (in a regular cycle) or in a cycle with hormones.  

You can see our results with frozen eggs, here.  

Unfertilised eggs 

Freezing unfertilised eggs can be done before cancer treatment or if you want to have an egg bank that can be used at a later date.   

Freezing unfertilised eggs without a medical reason is called social freezing. In social freezing, eggs may be stored for 5 years. When freezing unfertilised eggs, there is a risk that the eggs may be damaged during cryopreservation and thawing. This is because unfertilised eggs, due to their high water content (compared to fertilised eggs), are much more sensitive to the freezing process. However, techniques have improved significantly, and survival rates are around 70-80% for freezing and thawing in our clinics. We recommend freezing unfertilised eggs before the woman turns 36. You should expect about 20 unfertilised eggs on the freezer to have a good chance of pregnancy.   

Frozen unfertilised (young) eggs can increase the chance of pregnancy later in life but are not a guarantee.  

Importing unfertilised eggs into Denmark  

According to Danish legislation, unfertilised eggs can only be stored for 5 years after freezing. Therefore, we are unfortunately not able to receive unfertilised eggs that have been frozen for more than 5 years.  

When is freezing appropriate?  

In the context of fertility treatment (IVF/ICSI) 

It is often appropriate to freeze surplus fertilised eggs (ICSI) or in-vitro fertilisation (IVF). If necessary, these can later be thawed and used - e.g. if you want a second child. The advantage of freezing is that the woman does not need to have a new hormone treatment and egg retrieval.  


Want to know more about our services?


Let's talk fertility

Understand family growth options
in a consult with friendly TFP experts.