Embryos not used in the current cycle is often cryopreserved. Cryopreservation is often accomplished with vitrification, a speedy freezing method. Vitrification is assumed to circumvent cryoinjury by decreasing the event of intracellular crystals.[35] All embryos may also be frozen in patients at risk for ovarian hyperstimulation syndrome (reviewed further in https://www.ivf.com.mx/