Frozen Embryo Transfers
What is an FET?
Frozen Embryo Transfers (FETs) use embryos, unused and cryopreserved, from a previous IVF cycle. They are thawed, checked to ensure that they have survived and are growing, and transferred into your uterus. The resulting outcome will be the same as if it took place following a natural or IVF pregnancy.
The whole process is a lot simpler than its preceding IVF cycle as you do not need to take the follicular stimulating hormones that you previously self-injected to produce the eggs, and you do not need to have the operation to retrieve the eggs from your ovaries. Instead, you will take hormones to build your uterine lining in preparation for receiving the embryos. You will still need to be monitored by ultrasound to check progress.
If a woman finds the initial stages of IVF, up to egg collection, very stressful, she may choose not to have any embryos transferred at that time. Instead she may prefer to freeze all her embryos and have a FET a few months later in a more “normal” cycle. Forecasts are that in future this will be the recommended course of action for IVF cycles.
How Many Embryos Should you Transfer?
By law the maximum number of embryos you may transfer is two, or if you are over 40, three. Generally the transfer of only one embryo is strongly advised, to avoid the likelihood of twins.
The number of embryos transferred will depend on several factors: your age, the embryo quality and how many have survived the thaw.
Do you Thaw all Embryos?
Unused embryos can be frozen again but this should be avoided as there is no point in subjecting them to the extra stress. Instead we thaw only the ones required for transfer and we do this early enough so that, if they don’t survive, there is still time to thaw and check another before your transfer time. Any unused embryos can remain frozen until you need them. You may carry a pregnancy to birth, wait a while, and then have another FET to have a second child. Or a third, or fourth.
