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Freezing and storing embryos

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What is embryo freezing and storage?

Often with IVF or ICSI, people have a number of unused embryos after their first cycle. Some people choose to freeze them for use in later treatment cycles or to donate for use in others’ treatment, research purposes or training.

Your chances of becoming pregnant with a thawed frozen embryo are not affected by the length of time the embryo has been stored. But not all embryos will survive freezing and eventual thawing when they come to be used. Very occasionally no embryos will survive.

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Is embryo freezing and storage for me?

You may consider freezing your embryos for the following reasons:

  • It gives you the option of using the embryos in future IVF or ICSI cycles.
  • 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.
  • If you have a condition, or are facing medical treatment for a condition, that might affect your fertility (embryo freezing is currently the most effective way for women to preserve their fertility).
  • You are at risk of injury or death (eg, you’re a member of the Armed Forces who is being deployed to a war zone).
  • You are due to undergo a sex change operation.

For more information on preserving fertility if you have cancer see:

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What happens when embryos are frozen?

You and, if applicable, your partner will need to give written consent for your embryos to be stored.

Embryos will be created through IVF or ICSI and those of suitable quality will be frozen.

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

Before the storage process begins, your clinic 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.

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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.

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What happens when I want to use my frozen embryos?

The exact procedure for using your frozen embryos varies, depending on your personal circumstances and the type of treatment your clinic offers.

The initial steps depend on whether you are ovulating regularly. If your periods are regular and your clinic offers treatment every day, your doctor may suggest using a natural cycle. In this case, ultrasound scans may be used to check your developing eggs and the thickness of the endometrium lining of your uterus. Urine or blood tests may be used to check when you are ovulating (releasing an egg).

If your periods aren’t regular, or you don’t have them at all, your doctor may suggest you use drugs to suppress your natural cycle and trigger a ‘false’ period. You are then given medication to help prepare the endometrium lining for an embryo.

When the endometrium is at its most receptive, the clinic’s embryologist thaws the embryos. Up to three embryos may be transferred using the embryo transfer procedure described on p45. Your clinic will recommend single embryo transfer (SET) if they feel it is the best option for you due to the risks associated with multiple births.

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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.

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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.

The HFEA has not seen any evidence suggesting a risk to patients or to children born from frozen embryos. We will continue to review the evidence available on embryo freezing and the long-term results of frozen embryo transfer.

Clinics are required to offer counselling to all patients undergoing this process – it can be particularly helpful at this time.

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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 require 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, see:

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, see Research we have approved:

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

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What are freeze-all cycles?

Freeze-all cycles involve freezing all the embryos in a cycle and waiting to transfer them at a later date. Some people think that by giving the body time to recover from the fertility drugs it allows your uterus to return to its natural state and your chances of conceiving are higher. Research into freeze all cycles is progressing quickly although at the moment, doctors don’t know with enough confidence whether freeze all cycles are safer and more effective than conventional IVF or ICSI.

Couples having their first round of IVF treatment are invited to take part in a study into freeze-all cycles. More research may help us to determine whether freeze-all cycles genuinely increase your chances of having a healthy baby, with the potential to help tens of thousands of couples who have fertility treatment each year.

To find out more about the study and how to take part, download the resources below.

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Page last updated: 15 June 2015

Who offers embryo freezing and storage?

To find the clinic nearest to you that offers embryo storage, use the advanced search on our Choose a Fertility Clinic database.

What happens to your embryos in storage?

Follow the life cycle of eggs for freezing and storage - from when they are first stored to their eventual use.

Find out about storage time limits and how your eggs may eventually be used.

  • The embryo storage process