Embryos not used in the current cycle may be cryopreserved. Cryopreservation is usually achieved with vitrification, a rapid freezing approach. Vitrification is assumed to stop cryoinjury by lowering the development of intracellular crystals.[35] All embryos can also be frozen in patients in danger for ovarian hyperstimulation syndrome (mentioned additional in https://www.ivf.com.mx/