Embryo freezing has been used for many years, however the results obtained with conventional freezing techniques were bad, with very low pregnancy rates. It was identified that the formation of crystals inside the embryo was the cause of poor survival.
Vitrification is a freezing technique developed in order to avoid the formation of ice crystals, responsible for the destruction of cell membranes and potential damage of embryos. This technique has allowed to improve pregnancy rates when using cryopreserved embryos.
The vitrification is done when after a cycle of In Vitro Fertilization (IVF), embryos of good quality susceptible of preservation remain. These embryos may be devitrified and implanted in the future, in couples that consider the possibility of a second child, or a new chance of pregnancy if the first attempt has not concluded successfully, without the need for a new ovarian stimulation. It is also used in cases in which, for medical or personal reasons of the couple, the embryo transfer can not be carried out in the same IVF cycle.