Embryo freezing is the process of taking embryos at any different stage of creation and freezing them. Depending upon how many embryos are to be used for uterine transfer in the future, one or more embryos may be frozen together in a batch. After extraction from the uterus, the embryos are then mixed with a cryoprotectant to prevent damage to the embryo during the process. At that point, the embryos are stored in liquid nitrogen to keep them frozen and stored.
The process of freezing embryos has become wildly popular for patients that have made unsuccessful attempts at alternative fertility treatments. While most experts agree that the procedure is safe, there are some potential risks and complications that a patient should be aware of before electing embryo freezing.
Survival Rate
There are several processes that embryos have to go through in order to be kept frozen for future use. In order to do so, they are exposed to a variety of different toxins needed for freezing. While these toxins and cryoprotectants are essential for the freezing process to occur, there is the chance that some embryos make not be able to survive the process because of the drastic, unnatural changes that occur.
Every clinic is different in the survival rates that it boasts, but the average of intact embryos seems to be around 60%, with roughly 20% to 40% either not surviving or being damaged to the extent that they are no longer viable. It is important to keep in mind that the damage or lack thereof cannot be assessed until the embryos have gone through both the freezing and thawing stages.
Birth Defects
Although studies regarding birth defects of frozen embryo transfers are limited, some of them have suggested an increase in the occurrence of birth defects. The problem with these studies is that the process of freezing embryos is realistically only 26 years old. There is limited information on the followup of children born out of embryo freezing and implantation. As the years continue to pass and the children born from embryo freezing can be evaluated, there should be more structured, scientific information to prove or disprove this theory. In the meantime, it is simply important for patients be aware that there is a minute risk of birth defects with this process.
Disease and Infection
The embryo freezing process always takes place in a sterile laboratory environment; however, because these embryos are being transferred through the air into a contained environment, there is the very small potential of them coming into contact with pathogens in the air. Studies regarding this are also fresh and point toward this being an extremely rare occurrence. However, it is still a potential risk and should be explained to patients accordingly. Currently experts do not believe that this type of cross-contamination would affect a fetus brought to term, but rather that it might hamper the ability of the embryo to survive the freezing and thawing process.
