Cryopreservation involves slowly freezing embryos to store them for future use. This process involves a special liquid nitrogen freezer and the use of cellular antifreezes. The embryos are then stored, submersed in liquid nitrogen until they are thawed and placed into the uterus.
Not all embryos survive the freeze-thaw process. A 50% survival rate is considered reasonable. After the thaw, embryos retaining 50% or more of the cells they had before freezing are cultured and placed back into the uterus exactly like step four in in vitro fertilization.
Clinics all over the world have reported clinical pregnancies and normal live births. Embryo freezing in laboratory animals, as well as the experience with human embryos, has shown that the frequency of congenital anomalies or malformations in offspring is the same as that of the general population.
Embryo freezing is a new area in which legal principles and requirements have not been firmly established. Based on currently accepted principles regarding legal ownership of human sperm and ova, each embryo resulting from the fertilization of the wife’s egg and the husband’s sperm will remain with the couple, unless there is no legal marriage or husband, then ownership of the embryo resides solely with the woman signing the consent form. This principle may change at any time based upon the laws of the state or guidelines being revised.
Documents must be in place, which instructs the laboratory what to do if the wife can no longer have the embryos transferred into her uterus. Disposition of frozen embryos may also be subject to and controlled by final decisions of a court or other governmental authority having jurisdiction.