(Embryo cryopreservation)
Embryo freezing is a well-established form of assisted conception treatment. An increasing number of IVF clinics worldwide are now able to freeze spare embryos for later transfer. The first frozen embryo baby was born in 1984. Embryo cryopreservation allows multiple embryo transfers from a single egg collection and improves the chances of livebirth. The live birth rate from frozen embryo replacement equal to that of fresh embryo transfer (SART and HFEA 2018). This support the strategy of transferring one fresh embryo and freezing those remaining for future transfer.
Advantages of embryo cryopreservation
- Allow maximizing the potential for conception for IVF and prevent wastage of viable normal spare embryos. Perhaps this is the most important advantage of cryopreservation. Approximately 50% of women may have spare embryos available for freezing. In some clinics, the pregnancy and live birth rates with frozen-thawed embryo transfer is as high as those achieved with fresh embryo transfer.
- Freezing all embryos for subsequent transfer may be advised for women who are at a high risk of developing severe ovarian hyperstimulation syndrome following ovarian stimulation for in-vitro fertilization (IVF).
- When embryo implantation may be compromised in cases such as the presence of endometrial polyps, poor endometrial development, break through bleeding near the time of embryo transfer or illness.
- Difficulty encountered at fresh embryo transfer e.g. cervical stenosis (inability to pass through the cervical canal because the cervix is narrowed or scarred, etc).
- Cryopreservation of embryos is very important to be incorporated in the egg donation programs. It is not always possible to synchronize the recipient’s cycle with that of the egg donor. In some countries, it is mandatory to freeze all embryos created from donated eggs, quarantined for a period of six months and until the donor have a repeat negative screening tests.
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As a result of successful cryopreservation programs, frozen embryos have also become available for donation to infertile couples.
- Before cancer chemotherapy or radiotherapy.