Over the past decade, fertility doctors have increasingly used frozen embryos transfers as opposed to fresh embryo transfers. The vitrification, or freezing, of the embryos allows a patient more flexibility to save and transfer embryos at a later date. In addition, if a patient is interested in preimplantation genetic testing (PGT), it’s standard that the embryos will be sampled and frozen while the genetic testing is being completed. Once PGT results are reported, the patient and doctor can determine which embryo will have the best chance to result in a healthy baby, and thaw and transfer that embryo. Any remaining embryos can remain vitrified to use at a later date to grow the family.
Fresh Transfer vs. Frozen Embryo Transfer (FET)
When patients first learn about IVF, they are often surprised to learn that embryos don’t need to be transferred immediately after the egg retrieval and fertilization in the lab (fresh transfer).
Instead, embryos can be frozen after they are created and placed into long-term storage to be transferred at a later date. When the patient is ready for a transfer, one or two embryos can be thawed and transferred into the uterus with a frozen embryo transfer. Most IVF doctors agree that fresh transfers and frozen transfers have comparable success rates and some studies have found that success rates are increased with frozen embryo transfers.
Frozen Embryo Transfers
While both fresh and frozen transfers occur after stimulation, egg retrieval, fertilization of eggs in the lab, and growth of the embryos for a number of days, embryo vitrification and frozen embryo transfer allow greater flexibility to the patient. Before vitrification was available, patients had no option to save extra embryos and would need to discard any embryos they did not wish to transfer fresh immediately following their retrieval. Now, if an individual is able to yield multiple good-quality embryos with just one retrieval, the embryos can be vitrified and stored at the patient’s fertility clinic or at a cryo-storage facility. Each time the individual would like to add to their family, one or two embryos can be thawed and transferred with a frozen embryo transfer for years to come.
Embryo vitrification is a rapid freezing technique that involves just a few steps. The embryos are exposed to a cryoprotectant which prevents ice crystals from forming and harming the embryo. They are placed into storage straws and rapidly cooled and frozen with liquid nitrogen. The vitrified embryos are placed in cryo-storage containers, often called cryotanks. Liquid nitrogen is used to keep the embryos at a very cold temperature and cryotanks are monitored to ensure the temperature is maintained. It is worth noting that eggs, sperm, and embryos at many stages can be vitrified.
So, how long will my frozen embryo last?
Theoretically, frozen embryos are likely stable for decades or longer, maybe even indefinitely if their storage is well-maintained. Just last year, a couple had a baby from an embryo that was frozen in 1992. The embryo was transferred almost three decades after it was originally created and frozen. While there is a small risk that an embryo could arrest (stop growing) when it is being thawed prior to transfer, the vast majority of embryos are viable for transfer following the thaw or warming process. It is likely that your frozen embryos will remain viable throughout your family-building years and well beyond that if you choose to keep them stored.
Fertility treatment and reproductive medicine have come a long way since IVF was first introduced over 40 years ago. Today, advanced embryo testing is now available to couples who want their child to have the best shot of a healthy life. Explore how Orchid helps you conceive with confidence.