Depending on the number of embryos that were transferred to the uterus, this may leave a number of surplus additional embryos. These embryos may be preserved by cryopreservation (freezing) so that they may be transferred into the uterus in a future treatment cycle for another child or if the procedure is unsuccessful.
Frozen embryo transfer (FET) allows women to conceive in a future cycle without undergoing further ovarian stimulation and egg retrieval.
Embryos can be frozen at all stages of development, from zygote (fertilized egg) through cleavage stage (2-16 cells) (days 2-3) to blastocyst (days 5-6). Each embryo is placed into a specially designed sterile straw that is uniquely labeled. Straws containing the embryos are stored in liquid nitrogen for long-term storage (-196°C). A rapid cooling process called vitrification is now used in our lab almost exclusively. This has been shown to be the very best method of successful cryopreservation. Using this technique, the pregnancy results are now virtually the same as fresh embryos, and almost all embryos now survive freezing and thawing. There is no known time limit as to how long an embryo can be kept frozen and still result in a successful pregnancy.
Whenever it is decided to transfer frozen embryos, they are rapidly thawed. Despite the excellent results with vitrification, it is possible that some or all of the embryos will not survive the freeze, storage and thaw. It is only possible to determine which embryo(s) have survived once they have been thawed.
Once patients wish to have embryo(s) thawed and transferred, they will be given specific instructions regarding the medications necessary to prepare their uterus for the embryo(s).
Based on studies that have been performed in both animals and humans, the risk of birth defects in babies that develop from frozen embryos is no higher than in maternal age-matched naturally conceived pregnancies. The age-related risk of birth defects in babies that develop from frozen embryos is determined by the age of the woman from whom the eggs came at the time the embryos were frozen, not the woman’s age at the time the embryos are thawed and transferred.
If you choose not to freeze your excess fresh embryos for storage, they will be discarded unless you consent to donate them for research or anonymously for another couple. If you are considering donating your excess embryos, either to another couple or for research, you will be required to complete a consent form providing authorization and directions regarding their use.
You will be sent an annual invoice for storage after the first year. If you move or your contact information changes you must notify us. Once your family is completed and you do not wish to continue to preserve your excess frozen embryos, you will have the choice of discarding them, donating them for research or donating them to the clinic anonymously for another couple.