Frozen Embryo Transfer

Frozen Embryo Transfer

If you have surplus embryos after an IVF or ICSI cycle, they are frozen for future use in case that your treatment is not successful or for trying for a second baby.

Having embryos frozen means that you can undergo future cycles of IVF without having t stimulate your ovaries, collect and fertilise your eggs.  Instead, we can warm the frozen embryo(s) and transfer them to your womb in a much more simplified frozen embryo warming cycle.  This is what is commonly known as frozen embryo transfer (FET).

The frozen embryos can be in one of these two stages of development: cleavage stage (Day 3) or blastocyst stage (Day 5), depending on how long they had been cultured for before they were frozen.  In our lab, we tend to culture them till blastocyst stage for transfer on Day 5, but this may vary case to case.

The embryology team will talk to you about how many embryos would be more convenient to transfer in your case.  Whenever possible, we aim for an elective single embryo transfer (eSET) to reduce the chances of a multiple pregnancy and its complications.  Read more about eSET in our section about embryo transfer.

Your chance of becoming pregnant following a transfer of frozen-warmed embryos is comparable to that following a transfer of fresh embryos.  There is no evidence that any babies resulting from warmed embryos have an increased risk of abnormality.

It is also possible to bring your cleavage stage embryos or blastocysts frozen in another clinic for transfer at Cambridge IVF.

Frozen Cleavage stage embryo transfer

Not all the embryos survive the process of freezing and warming, particularly those that are not of good quality, as these processes can cause damage to the cells of the embryo.  To maximize survival rates, we only select very good embryos.

When we warm cleavage stage embryos we assess them for cellular damage immediately after.  We will call you on the day of your transfer to let you know how many embryos survived the warming.  If we need to, we will warm an additional straw to ensure you have the agreed number of blastocysts for transfer.

Once the embryos are warmed, we place them in culture medium for approximately 2-3 hours to regain their shape and recover from the warming process.  After this time, we can perform the transfer.

Frozen blastocyst transfer (FBT)

Freezing and warming can cause damage to the cells of a blastocysts (advanced 5 to 6-day embryos), particularly those which are not good quality; for this reason, we only select very good quality blastocysts for freezing.

When we warm blastocysts we assess them for cellular damage immediately post warm. Our data from warming procedures performed at Cambridge IVF on vitrified blastocysts tells us that over 90% of all warmed blastocysts survive the procedure and are suitable for transfer.

We will call you on the day of your blastocyst transfer to let you know how many blastocysts survived the warming.  If we need to, we will warm an additional straw to ensure you have the agreed number of blastocysts for transfer.

Once the blastocysts are warmed, we place them in culture medium for approximately 2-3 hours to re-expand.  After this time, we can perform the transfer.

What should I expect on the day?

You should bring your partner or a friend with you as we would prefer you to have a chaperone and someone to take you home after the procedure.

We will confirm with you the number of embryos we are transferring and let you know the quality.  We will then ask you to sign the consent prior to the embryo transfer taking place.  You also have the option of seeing the embryos on the screen before we transfer them if you like.

Then you will lay down and one of our Embryologists will bring the catheter containing the embryo(s) to be transferred.  The consultant will introduce the catheter through your cervix and place the embryo(s) at the fundus of the uterus using an ultrasound to guide him/her.

Finally, the Embryologist will take the catheter back to the lab to check that the catheter is clean, meaning that the embryos have been correctly introduced into your uterus and are not in the catheter

What should I do after?

You do not need to rest after the transfer.  Lying on your back for days afterwards will not help the embryo(s) implant and in truth may do more harm than good.  We recommend you take things easy, so no parachute jumps or horse riding, but just try to carry on with your life as normal otherwise.

You can have your pregnancy test on the date established by your consultant.  This is usually done 15 days after your transfer.

If you would like more information, please contact us.