With the level of technology available in the world today, oocyte cryopreservation is still experimental. It is however possible to preserve the sperm and embryo by freezing and storing them i.e. Cryopreservation. Donor sperm and embryo are preserved till they are needed through this procedure.
Donor sperm : is mixed with special culture medium to prevent the semen from being damaged during freezing, the mixture is loaded into plastic straws which are loaded and sealed. The straws are frozen in liquid nitrogen at -196C till they are required when they are thawed. It is however known that the quality of semen may be reduced after freezing.
Embryo cryopreservation: The first frozen embryo baby was born in 1984. Though an increasing number of clinics worldwide are now able to freeze spare embryos for later transfer, not all clinics offer freezing facilities.
Advantages of embryo cryopreservation:
Prevents wastage of viable normal spare embryo thereby maximizing the potential for conception of IVF. About 40 – 50% of women may have spare embryos available for freezing. Though the overall success rate with the use of cryopreserved embryos is believed to be lower than with the use of fresh embryos. It is known that in some clinics, the transfer of frozen embryos results in same pregnancy and live birth rates with the use of fresh embryos especially with the use of Laser Assisted Hatching.
Freezing of embryos may be advisable for women at a high risk of developing severe OHSS following ovarian stimulation for IVF.
When the presence of conditions like endometrial polyp, poor endometrial development, breakthrough bleeding near the time of embryo transfer may compromise embryo implantation.
The presence of severe cervical stenosis leading to difficulty in fresh embryo transfer.
In egg donor programs, when sometimes it is not possible to synchronize the recipient’s cycle with that of the egg donor . The eggs can be fertilized and the resultant embryos stored for future use.
Frozen embryos can be donated to infertile couples.
It is important to state that babies born following embryo freezing have no increased rate of abnormalities as those born following IVF and that only embryos of good quality can be frozen.
