Information sheet - Embryo freezing

Following an in vitro fertilisation (IVF) or intra-cytoplasmic sperm injection(ICSI) treatment cycle, where fertility drugs stimulate the ovaries to produce more eggs than usual, there may be some good quality unused embryos which are suitable to freeze for future treatment cycles if conception is not successful, for a sibling pregnancy, or to donate to another woman.

We use state-of-the-art vitrification technology to freeze embryos, which are kept in liquid nitrogen storage at -196°C. At this temperature, all biological activity in the embryo stops and the embryos will be stable for many years.

Current regulations allow us to store embryos for up to 10 years (or with special consent up to 55 years) and these can be used at a later date in frozen embryo transfer (FET) cycles.

What are the advantages of the embryo freezing procedure?
  • If you have a regular cycle, embryos can be transferred during a natural cycle.
  • If you have a regular cycle, embryos can be transferred during a natural cycle.Therefore, there is no need to take any drugs or go through the egg collection procedure as in IVF and ICSI
  • If you have an irregular cycle then you will need to take some medication which is usually by mouth rather than injections. However, the drug administration for this procedure is not as intensive as an IVF or ICSI cycle, and there is no egg collection operation
  • Whilst information is still limited, there appears to be no increased risk of abnormalities in babies who have developed from frozen/thawed embryos compared to a transfer of fresh embryos
What are the disadvantages?

There is a cost for freezing, thawing and transfer, as well as an annual storage fee (see price list for current costs)There is a cost for freezing, thawing and transfer, as well as an annual storage fee (see price list for current costs)• The chance of a pregnancy using frozen/thawed embryos is less than that when transferring fresh embryos. As a guide, it is around 20% less than the quoted fresh transfer pregnancy rate• There is no guarantee that an embryo will survive the freezing and thawing and, even if it does survive, it may not continue to develop or result in a pregnancy• Not all embryos will be of sufficient quality to be considered for freezing

Can I control what happens to my frozen embryos?

If you decide to have your surplus embryos frozen, we will ask you to sign some consent forms that mean you decide:If you decide to have your surplus embryos frozen, we will ask you to sign some consent forms that mean you decide:• How long you would like the embryos to be stored• What would happen if you (or your partner) died or were unable to make a decision for yourself• Whether the embryos will just be used for your own treatment, or whether you would like to donate some to another woman or for research• Any other conditions that you would like to include about how your embryos are usedYou (or your partner) can withdraw your consent either before treatment or before embryos are donated to another woman or for research. If one of you withdraws your consent then you have up to a year to decide what should happen to the embryos that are not used.

Pronucleate Embryos

An embryo at the ‘Pronucleate’ stage has only one cell. This stage occurs about 16-20 hours following the egg collection (i.e. the morning after egg collection). No grading of the embryo can be made at this time. Embryos frozen at this stage of development tend to survive the freezing and thawing process better than at any other stage as the cells are not in the middle of division processes.
This is generally reserved for patients who will not be having a fresh transfer such as those who require freezing for chemotherapy reasons. It is generally not used for patients with a fresh transfer as it is not possible to distinguish between embryos at single cell stages.

Cleaved Embryos

Following embryo transfer (up to 5 days after egg collection), any remaining embryos of grade 1 or 1-2 can be frozen. Only very good grade embryos will be frozen, because poorer grade embryos are unlikely to survive freezing and thawing.

Are there any risks to children born from frozen embryos?

So far, there has not been any evidence to suggest that children born from frozen embryos are at more risk than other children. However, since this is a relatively new technique, longer term research is still being carried out.

How secure is the storage system?

We use an ‘electronic witnessing system’ which matches each patient and their partner (or donor) with a number and barcode that is also used to tag their embryos. This unique numbering and barcode system ensures that mistakes cannot be made.

What to do next

You will need to complete and sign:You will need to complete and sign:• HFEA consent form MT for maximum storage of 10 years• HFEA consent form WT for maximum storage of 10 years• The Agora Embryo Freezing AgreementPlease note: you will be asked to sign HFEA consent forms for 10 years. You will have an annually updated agreement to store embryos for up to 10 years with the Agora Fertility Centre. If you require storage to 55 years (this can only be for your own use) you will be required to extend your Agora contract and discuss the requirement with the Laboratory Manager or your consultant at the end of the first 10 years.Every year the Agora Clinic will send you an update form that must be completed and returned. This tells us what to do with your embryos. An invoice for the annual storage will be sent along with this.It is essential that you inform the Agora of any change in address or circumstances, as lost contact could result in your embryos being discarded.

DisclaimerThe medical information provided here is as an educational resource only.

It is not intended to replace the advice of your GP or medical team and should not be used or relied upon for any diagnostic or treatment purposes.

The information has been prepared by Dr Carole Gilling-Smith, Consultant Gynaecologist and Medical Director of the Agora Gynaecology and Fertility Centre.

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