What is Embryo freezing?
Embryo freezing is a process that involves freezing and storing unused embryos. These embryos consist of fertilized eggs created during IVF, including intracytoplasmic sperm injection (ICSI). Researchers use a technique called cryopreservation, starting the process with freezing.
The clinic stores the frozen embryos and can thaw them when needed for future IVF cycles. This helps patients save time and money. The woman will not need extra egg retrievals or as many medications in future cycles.
People usually choose to freeze their embryos to keep the option of becoming a parent later. Reasons for considering cryopreservation include cancer treatment, ageing, or the risk of injury from medical conditions or military deployment.
How are embryos frozen and stored?
Reproductive endocrinologists use two methods to freeze embryos: vitrification (flash freezing) and slow programmable freezing. While these methods differ, both involve cooling the embryos with cryoprotectants or "antifreeze" fluids. Since embryos mostly contain water, freezing can cause ice to form and damage the cells when someone thaws them. Cryoprotectants help prevent ice crystals from forming, protecting the embryos from harm during the freezing process.
In the slow-freezing method, embryologists place embryos in a machine that cools them gradually in stages. After adding cryoprotectants, the embryos are frozen and stored in liquid nitrogen at -321°F. This process takes about two hours.
Vitrification, a newer and more successful method, uses a solution with a higher concentration of cryoprotectants. Researchers quickly freeze the embryos in liquid nitrogen, turning them into a glass-like substance. This process prevents ice crystals from forming, improving the chances of the embryo's survival and viability after thawing. At Arockia Virgin Fernando Clinic, the staff exclusively uses vitrification for the cryopreservation of all new embryos.
No matter the method, frozen embryos remain paused in time. All biological activity, like cell growth and death, stops.
When needed, someone gently thaws the embryos and soaks them in fluids. This process removes the cryoprotectants and adds water back to the cells. People can store frozen embryos for a long time. Researchers stored the longest frozen embryo for 19 years, which led to a healthy pregnancy.
What are the risks of freezing embryos?
Research shows that freezing and thawing embryos does not harm babies born through IVF. Storing an embryo for a longer time does not impact the success rates of IVF.
With advancing technology, the difference in pregnancy rates between frozen and fresh embryos is now minimal. The stimulation process for frozen embryo transfer is gentler. Hormone levels are closer to normal, which may help improve pregnancy rates.
Ice crystals that form when freezing slowly can harm an embryo during thawing. This is one reason why vitrification is the preferred method for cryopreservation. Research shows that children born from frozen embryos do not have a higher risk of congenital disabilities. This is the same for those born from fresh embryos.