Oocyte/embryo cryopreservation is a process where oocytes/embryos are immersed in a series of solutions which dehydrate the cells and replace the water molecules with cryoprotectant, thereby protecting the integrity of the cells during the freezing process. The oocytes/embryos are loaded into specially designed straws, and placed into liquid nitrogen tanks for long term storage. These frozen oocytes/embryos may be subsequently thawed and used for a future embryo transfer. Not all patients undergoing IVF will have embryos for freezing. Surplus embryos remaining after embryo transfer are evaluated, and if they have advanced appropriately, they may be frozen.
The two primary methods used in the industry for freezing are slow freezing and vitrification. CNY Fertility Center now performs vitrification as our method for cryopreservation. Indications for egg/embryo cryopreservation include:
Preserving surplus embryos following embryo transfer which may be used in the future to achieve a pregnancy. By transferring frozen-thawed embryos into the uterus, it is possible to achieve 2 or more pregnancies in different years from a single egg retrieval
Preserving fertility in patients who must undergo medical treatments such as chemotherapy for cancer treatment which may affect fertility. By undergoing IVF with embryo freezing, the couple/individual may thaw and transfer cryopreserved embryos following successful treatment.
Oocyte (egg) freezing is currently considered investigational as eggs are much more delicate than embryos when it comes to the freezing and thawing process. Although significant advances have been made in the technique, success rates are still lower than those from embryos. Oocyte freezing may be an option for long term fertility preservation in situations where a female may require cancer therapy treatment, but currently does not have a partner and chooses not to fertilize her eggs with donor sperm. CNY Fertility center is currently performing oocyte cryopreservation on an investigational basis as recommended by ASRM.