Vitrification for Embryos and Eggs


Vitrification, a cutting edge technology for cryopreservation (freezing) of embryos and eggs, is now available at CNY Fertility Center.
Patients who undergo IVF may have several eggs collected. The eggs are then fertilized with a sperm and checked for fertilization. Fertilized eggs are called embryos. A patient may have multiple high quality embryos eligible for embryo transfer back to the uterus. A certain number of embryos are chosen for embryo transfer, and the surplus of high quality embryos are able to be cryopreserved for future use.
Previously, embryos were cryopreserved using a slow freeze method. Embryos were run through different solutions of media to dehydrate the cells of water and replace it with cryoprotectant. Then the cryoprotected embryos were individually labeled and stored in cryopreservation straws, which were put in special freezers. These freezers slowly (-0.3 degrees Celsius per minute), cooled the embryos to -35 degrees Celsius using liquid nitrogen. They were then stored in liquid nitrogen (-196 degrees Celsius). At that extremely cold temperature, cellular activity is essentially brought to a halt, allowing the embryos to remain viable indefinitely.
When patients decide to use their cryopreserved embryos to try for a pregnancy, the embryos are removed from the liquid nitrogen, warmed and run through solutions of media to remove the cryoprotectant and rehydrate the cells with water. During cryopreservation, the formation of intracellular ice crystals can damage the cells of the embryo, decreasing future viability. Therefore, new methods were developed to improve cryopreservation techniques.
Vitrification is a new process for cryopreserving embryos. Through vitrification, the water molecules in an embryo are removed and replaced with a higher concentration of cryoprotectant than in the slow freeze method. The embryos are then plunged directly into liquid nitrogen. This drastic (-12,000 degrees Celsius per minute) freezing creates a glass transition temperature, commonly called a “glass” state, and the embryos are vitrified. This quick freezing reduces the chance for intercellular ice crystals to be formed, thus decreasing the degeneration of cells upon thawing for embryo transfer.
Many studies show survival rates of vitrified embryos to be far higher than survival rates of slow freeze embryos. Thus far at CNY Fertility Center, vitrification results are very encouraging, and we are excited to offer this cutting edge technology to all patients who chose to cryopreserve their embryos.
To date there has been limited success with eggs surviving after the cryopreservation and thaw process. Eggs have a much larger volume of water than embryos. The large water component of an egg increases the formation of intracellular ice crystals during the freezing process, which causes degeneration. Vitrifying eggs reduces the occurrence of intracellular ice crystals, which improves freeze, thaw and pregnancy outcomes. This new technology allows women to preserve their fertility by freezing eggs at a younger age, and using them in the future.
For more information about vitrification, ask to speak to an embryologist at your center.