Freezing tissue is called cryopreservation. Cryopreservation is a special process that makes it possible to store cells and tissues over a long period of time for later use. Cells and tissues are frozen and stored at minus 196 degrees Celsius in liquid nitrogen. The name of this technique comes from the ancient Greek word “cryos”, which means “cold”.

Freezing can be used for sperm, unfertilized eggs, fertilized eggs and tissue from the ovary/testicle ​

Sperm from male partner: It is possible to get frozen sperm at the clinic. We recommend this if in the event of the partner’s prolonged absence, illness or the man’s inability to provide a sperm sample on command (psychological impotence).

Donor sperm:
All donor sperm is frozen when we receive it at the clinic. This is due, among other things, to a statutory quarantine of donor sperm before it can be used.

Fertilized eggs:
We recommend freezing excess fertilized eggs after ICSI/IVF.
The freezing and thawing procedure 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 just as good when using frozen eggs as with fresh treatment. The advantage of freezing is that the woman does not need to undergo a new hormone treatment and egg retrieval. Egg freezing can be done during the woman’s own cycle (with a regular cycle) or during a cycle with hormones.

See our results with frozen eggs here.

Unfertilized eggs:
Freezing unfertilized eggs can be done before cancer treatment or if you want to have an egg bank that can be used at a later time.

Freezing unfertilized eggs for no medical reason is called social freezing. With social freezing, the eggs must be stored for 5 years. When freezing unfertilized eggs, there is a risk that the eggs may be damaged during cryopreservation and thawing. This is because unfertilized eggs, due to their high water content (compared to fertilized eggs), are much more sensitive to the freezing process. However, the techniques have improved significantly and survival is around 70-80% when freezing and thawing in our clinics. We recommend freezing unfertilized eggs before the woman turns 36. You have to count on around 20 unfertilized eggs in the freezer to have a good chance of pregnancy.

Freezing unfertilized (young) eggs can increase the chance of pregnancy later in life, but is not a guarantee.

When is freezing appropriate?

It is often appropriate to freeze excess fertilized eggs (ICSI) or in-vitro fertilization (IVF). If necessary, these can be thawed and laid out – e.g. upon request for another child. The advantage of freezing is that the woman does not need to undergo a new hormone treatment and egg retrieval.

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