Medical science has maintained laboratories for assisted reproductive technology or ART to successfully frozen sperm, even eggs, and embryos known as Frozen Egg Bank. Though, success within this environment is a relative term from a historical perspective. The freezing of sperm egg, for example, worked well for several decades with little technological adjustment to the basic freezing protocols. This is possibly happened as sperm do not have that much of water in their composition if it has the more water the greater that freezing damage will happen.
Embryos composition has higher water, and has been harder to freeze and defrost successfully. Since 25 years, live birth rates from thawed embryos have increased from 5%. In such programs, there is a little difference from results achieved with the transfer of non-frozen embryos in all patient categories.
Sperm have been on the whole challenging because they acquire unique structures that are very prone to freezing injury. With that said, thawed eggs too have started to contribute radically to live births from assisted reproductive technology the world over. This helps in increasing live birth rates for thawed embryos and eggs happened during incremental refinements i.e. “controlled rate” freezing, a process of slowly lowering the temperature of the freezing composition that embryos are immersed in over a long-hour period. The frozen solutions are then kept into liquid nitrogen storage tanks where they will remain sometimes for many years until they are needed.
Recently, an important technological allows extremely quick freezing of eggs and embryos. And this known as a new method of “flash freezing” or vitrification appears to lower the chances of freezing damage, and therefore it has the potential of higher pregnancy rates than controlled rate method. It is safe, non-injurious freezing methods of all types are avoidance of the development of ice crystals forming inside the solutions, be they eggs, sperm or embryos. The flash freezing method minimizes ice crystal formation, and is thus an inherently safer approach.
In fact, the survival rate upon thawing of flash frozen eggs is so high more than 95% usually that it is now possible to bank eggs removed and frozen from anonymous donors. The potential recipients may select from a catalog containing information about the egg donor comparable to what one finds with Frozen Donor Egg bank. Just for the patient convenience and safety, this represents a extensive change from the past, that brings the practice of unknown egg donation into compliance with tissue banking laws that are applied to each type of sperm banking.
After long period of evaluative studies of the best tissue freezing methods currently available, reproductive Center or ART is well into the process of transition from controlled rate to tissue freezing through blastocyst stages.