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Embryo Freezing

What is embryo freezing and storage?

During in vitro fertilisation (IVF) or intra-cytoplasmic sperm injection (ICSI) treatment, fertility drugs are used to stimulate the ovaries to produce more eggs than usual. These are then fertilised with your partner's, or a donor's sperm to create embryos.

Because there is normally a number of unused embryos, some people choose to freeze the good quality unused embryos for use in later treatment cycles or for donation. 

Is embryo storage for me?

You may consider freezing your unused embryos for the following reasons:

  • It gives you the option of using the embryos in future IVF or ICSI cycles, without having to go through the risks, expense and inconvenience of using fertility drugs and undergoing egg collection again.
  • If your treatment needs to be cancelled after egg collection (for example, if you have a bad reaction to fertility drugs), you may still be able to store your embryos for future use.
  • You want to donate your unused embryos for the treatment of other women or for research.
  • You are facing medical treatment, such as for cancer, that may affect your fertility, (embryo freezing is currently the most effective way for women to preserve their fertility).

How much control do I have over what happens to my embryos?

Before the storage process begins, we will ask you to sign consent forms. The forms allow you to specify:

  • How long you want the embryos to be stored (the standard period is ten years).
  • What should happen to your embryos if you or your partner were to die or become unable to make decisions for yourself.
  • Whether the embryos are to be used for your own treatment only, or whether they can be donated for someone else's treatment, or used for research.
  • Any other conditions you may have for the use of your embryos.

Withdrawing consent

You, your partner or the donor(s) can vary or withdraw consent at any time, either before treatment or before the embryos are used in research. It is important to understand that, if this happens, your embryos will not be used in treatment or research.

If one person withdraws consent (either the person who provided the eggs or the sperm) then there will be a 'cooling-off' period of up to a year which will allow you to decide what should happen to the embryos.

If you are not continuing treatment, you may want to consider donating your unused embryos.


What is my chance of having a baby using frozen embryos?

Due to the freezing and thawing process, your chances of having a baby using a thawed frozen embryo are lower than with a fresh embryo.

Your chances of becoming pregnant with a thawed frozen embryo are not affected by the length of time the embryo has been stored for.


What are the risks of freezing embryos?

  • Not all embryos will survive freezing and eventual thawing when they come to be used.  Very occasionally no embryos will survive.
  • It is not uncommon for those embryos that do survive freezing and thawing to lose a cell or two. Ideally the embryos should continue to divide between thawing and transfer.
  • As embryo transfer is involved in using frozen embryos, the same risks apply.

To date, there is no known evidence to suggest a risk to patients or to children born from frozen embryos. The Human Fertility and Embryology Authority (HFEA) will continue to review the evidence available on embryo freezing and the long-term results of frozen embryo transfer.

All patients undergoing this process are advised to access our Counselling Service, as it can be particularly helpful at this time.


How are donated frozen embryos used?

Your embryos can only be donated if the people who provided the sperm and eggs which were used to create the embryos - you, your partner (if you have one) and any donor(s) - give their consent to this in writing. Once you have given your consent, they may be used for three purposes:


  • In another person's fertility treatment

If you donate your embryos to another person to be used in treatment, the same rules on donation apply as to donating sperm or eggs. You will both need to have further screening tests for cystic fibrosis, karyotype (chromosome analysis), cytomegalovirus, syphilis and gonorrhoea.  In addition your blood groups will be checked.

Any child born from your donation will be able to find out identifying information about you when they reach the age of 18. For more information, click here.

If you are donating embryos to a single woman who has agreed to have parental responsibility, the sperm donor may be regarded as the legal father of the child. It is therefore very important that you fully discuss this aspect with your consultant. You may need to consider obtaining legal advice over this.


  • For research

If you donate your embryos to research, they could be used in studies, such exploring IVF technology, or in stem cell studies. For more information on research projects currently licensed by the HFEA, click here.


  • For training

If you donate your embryos to training, they could be used by trainee embryologists in order to practise techniques such as freezing embryos and removing cells from embryos.

Please note:  It is important that all couples with frozen embryos stored at Saint Mary's Hospital inform us about any changes in their contact details.  This is because we are required by law to contact you regarding the continued storage of your embryos for the consented period.


For more information please visit the HFEA website: http://www.hfea.gov.uk/.


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