Cryopreservation
Freezing Technology
Freezing and "storage" of human cells and tissues is carried out at low temperatures. The use of liquid nitrogen enable such temperatures (-196°C) to be reached. These conditions allow for the cryogenic storage of, for instance, unfertilized oocytes, spermatozoa as well as fertilized oocytes and embryos over a longer period of time, without their viability and functioning thereby being compromised. Aseptic vitrification (Learn more) is a modern and innovative technology.
1. "Situations where it is beneficial to opt for cryopreservation"
2. Cryopreservation of sperm and testicular tissue
3. Cryopreservation of unfertilized oocytes
4. Cryopreservation of fertilized eggs
5. Cryopreservation of embryos at different stages of development
1. "Situations where it is beneficial to opt for cryopreservation"
... as part of the fertility treatment
During fertility treatment, situations may occur requiring the freezing of fertilized egg cells and embryos at various stages of their development, for example as in the following situations:
- poor endometrial response (insufficient thickness of uterine lining) to hormonal stimulation, leading to postponed embryo transfer
- occurrence of ovarian hyper stimulation syndrome (OHSS)
- in the context of genetic testing by means of PGD/PGS (here, new terms are used at international level: PGT-A, PGT-M, PGT-SR)
- when performing "Single-Embryo Transfer", i.e. any supernumerary embryos remaining from a fresh cycle, apart from the embryo(s) to be transferred (maximum of 2) will be cryopreserved.
- primary frozen embryo transfer
... for "Fertility Preservation"
In such cases, precautionary measures are taken to overcome the age-related decline in fertility or preserve the reproductive options of patients with malignant diseases, for instance, as in the following situations:
- before undergoing radiation or chemotherapy
- childbearing tends to be postponed until later ("Social Freezing")
2. Cryopreservation of sperm and testicular tissue
Sperm can be retrieved from the semen after ejaculation, from the epididymis or testis. Those spermatozoa can be frozen and stored until needed for use in future assisted reproductive procedures. It makes sense for male cancer patients of reproductive age to bank sperm before undergoing chemotherapy or radiation. Thus, they can later use the sperm to induce a pregnancy through medically assisted reproduction, should their testicular tissue be damaged during cancer treatment. Scientific evidence suggests that the storage period has no effect on sperm quality. Donor sperm, too, can be frozen and stored. After cryopreservation, the donor is screened once again within a set period of time for specific infectious disease markers. This is done in accordance with legal requirements. Only if all the tests come back negative, the semen sample is released.
3. Cryopreservation of unfertilized oocytes
In medical situations where a woman's oocytes are in danger of being damaged, e.g. by an upcoming radiotherapy or chemotherapy, or due to the postponement of childbearing for social reasons, the cryopreservation of oocytes may often turn out to be a wise precaution. (See "Fertility Preservation").
4. Cryopreservation of fertilized eggs
The freezing of ova in the pronucleus stage (zygote) on day 1 of their development is considered to be safe and reliable. Very good results can be achieved regarding post-thaw viability and blastocyst development.
5. Cryopreservation of embryos at different stages of development
Any healthy embryos resulting from an IVF cycle that were not used in the first embryo transfer (a maximum of 2 embryos can be transferred at a time) shall be cryopreserved. Embryos can be frozen at any stage of their development (from day 2 up to day 6). Both slow freezing and a method termed "vitrification" (rapid freezing using liquid nitrogen) have been successfully applied for many years in our IVF Centers.