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Embryo freezing
Some people who are having fertility treatment have embryos which are not transferred in their IVF cycle. Find out how your embryos can be frozen for use in later treatment or to donate to research, training or someone else.
Why do people freeze embryos?
Often with in vitro fertilisation (IVF) or Intracytoplasmic sperm injection (ICSI) treatment, there may be some good quality embryos left after embryo transfer. Instead of disposing them, there is the option to freeze them to use in the future (in case treatment doesn’t work for example, or to try for a sibling).
Embryos can also be frozen to preserve fertility so it may be possible to have a baby at a later date.
Is embryo freezing for me?
You may wish to consider freezing your embryos if:
- You want the option of using your embryos in the future (rather than having a further fresh IVF or ICSI cycle).
- Your treatment needs to be cancelled after egg collection (for example, if you over respond to fertility drugs). You should be offered the opportunity to have any suitable embryos frozen to use later.
- You have a condition, or are facing medical treatment for a condition, that might affect your fertility. (Fertility may be preserved either by storing eggs, embryos or a combination of both. Please note that, depending on where you live, you may not be able to have embryo freezing on the NHS.
- You are at risk of injury or death (for example you’re a member of the Armed Forces who is being deployed to a war zone) and you want to create and freeze embryos with your partner.
- If you're a female transitioning to a male, you may want to preserve your fertility before you start hormone therapy or have reconstructive surgery. Both treatments can lead to the partial or total loss of your fertility. Read more information for transgender and non binary people seeking treatment.
Find out more about preserving your fertility.
There is no evidence to suggest that embryos are affected by the length of time they are frozen for.
What happens when embryos are frozen?
Firstly, you’ll need to be tested for any infectious diseases like HIV and hepatitis. Not all embryos are suitable for freezing so only good quality embryos will be chosen to freeze. Embryos can be frozen at different stages of their development – when they’re just a single cell, at the two to eight cell stage or later in their development (called the blastocyst stage).
Find out more about the development stages of embryos.
The embryos are put in a special solution containing substances (cryoprotectants), which help to draw water out from the embryo and provide protection in the cells. This protects them from damage caused by ice crystals forming. They’re then frozen, mostly by a technique called vitrification (fast freezing) and stored in tanks of liquid nitrogen until you’re ready to use them.
How long can I store my embryos for use in treatment?
If your embryos are not used immediately in treatment, you may wish to store them so they can be used for treatment in the future. To be stored embryos are frozen. You will need to think about how far in the future you might want or be able to use stored embryos and the potential costs of storing. This is something you should discuss with your clinic.
You should be aware that embryos can only be stored if both you and the egg or sperm provider have given consent. This may be your partner, or it may be a donor (if donor sperm or eggs have been used in your treatment).
On 1 July 2022, the rules on how long you can store eggs, sperm or embryos changed. Before 1 July 2022, most people could usually only store their embryos for up to 10 years. Only if they had premature infertility or were going to be having medical treatment which could affect their fertility, could they store for up to 55 years.
The law now permits you to store embryos for use in treatment for any period up to a maximum of 55 years from the date that the embryos are first placed in storage. However, crucially for storage to lawfully continue you will need to renew your consent every 10 years. You must give your consent on the relevant consent form. You will be contacted by your clinic with relevant information and they should also provide you an offer of counselling before you give consent to storage of your embryos. Your clinic will contact you and provide the consent forms that you need to complete at the appropriate time. It is therefore essential that you keep your contact details up to date with your clinic as you will need to be contacted. If your clinic is unable to contact you your embryos will be at risk of being removed from storage and disposed of.
You don’t have to match the length of storage to any contract for paying for the storage (whether you, or the NHS, is paying). However, if you don’t pay for storage as agreed, the clinic may be within its right to dispose your embryos. Your clinic should have explained this to your clearly when you stored your embryos.
What happens if I do not renew my consent to storage at the appropriate time?
If you do not renew your consent to storage your embryos will be removed from storage and disposed of when they no longer can be lawfully stored.
If you do not wish to renew your consent to storage or to continue storing your embryos then you can withdraw your consent to storage . You will need to contact your clinic and complete the relevant withdrawal of consent form. At this point you may wish to consider donating the embryos that you do not wish to use for your own treatment for training purposes, or for use in someone else’s treatment. You would need to discuss this with your clinic and provide the additional consents where relevant. You can also consider donating your embryos for use in research, helping to increase knowledge about diseases and serious illnesses and potentially develop new treatments. Your clinic will need to give you more information about this and advise you whether this is an option for you.
I stored my embryos before 1 July 2022, what should I do?
If you stored your embryos before 1 July 2022 for up to 10 years and would now like to store for a longer period (up to a maximum of 55 years from the date that the embryos are first placed in storage), you should contact your clinic to discuss whether this is possible and provide the additional consents where relevant.
If you previously consented to store your embryos for longer than 10 years (up to a maximum of 55 years) because of premature infertility or because you were going to be having medical treatment which could affect your fertility you should contact your clinic as soon as possible as consent will now have to be renewed at each 10 years. You and the sperm or egg provider will need to complete additional consent forms in order for your clinic to legally continue to store your embryos (even if the clinic are still storing your embryos within the consent period you originally specified). Your clinic will know the date when you must complete and return the relevant consent form for storage to continue. If you do not renew your consent the embryos will be removed from storage and disposed of.
Keep your contact details up to date
Make sure you tell your clinic if any of your contact details change. Because your clinic needs to contact you about your consent to storage, you should always inform your clinic if your contact details change or if your circumstances change (eg, in the event of separation from your named partner). If your clinic is unable to contact you to obtain your consent, then your embryos will be removed from storage and disposed of when they can no longer be lawfully stored.
How much control do I have over what happens to my embryos?
Before your embryos are frozen, it’s very important you give your informed consent by signing the relevant consent forms. These will explain:
- how long you want the embryos to be stored for
- what should happen to your embryos if you were to die or become unable to make decisions for yourself
- whether the embryos are to be used and stored for your own treatment only, or whether they can be donated for someone else’s treatment, or used and stored for training or research
- any other conditions you may have for the use of your embryos.
What if one of us changes our mind about using or donating embryos?
You, your partner or the donor(s) (if applicable) can vary or withdraw consent at any time before the embryos are used in treatment or research. If your partner withdraws their consent then your embryos cannot be used in treatment.
If one person withdraws consent (either the person who provided the eggs or the sperm) then there maybe a ‘cooling-off’ period of up to a year. If after this time your partner or the donor(s) till doesn’t want the embryos to be used, they’ll be removed from storage and allowed to perish.
What happens when I want to use them?
The exact procedure for using your frozen embryos varies depending on your personal circumstances and your clinic.
The initial steps depend on whether you are ovulating regularly. If your periods are regular, your doctor may suggest having the embryo transferred to your womb with no fertility drugs. In this case, ultrasound scans may be used to check the lining of your womb. Urine or blood tests may be used to check when you’re ovulating (releasing an egg), which indicates that the lining of your womb will be ready to receive the embryo.
If your periods aren’t regular, or you don’t have them at all, your doctor may suggest using drugs to suppress your natural cycle and trigger a ‘false’ period. You are then given medication to help prepare the womb lining for an embryo.
When the timing’s right, the clinic’s embryologist (embryo specialist) will thaw your embryos and usually transfer one embryo to your womb (three embryos can be transferred in exceptional circumstances if you’re over 40).
How successful is embryo freezing?
Success rates for IVF using frozen embryos have been increasing year on year.
For the latest statistics on surgical embryo freezing, visit our Research and data page.
Does freezing damage the embryos?
Sadly, not all embryos will survive the freezing and thawing process and very occasionally no embryos will survive.
It’s not uncommon for those embryos that do survive to lose a cell or two. In many cases the embryo will recover and continue to develop. The clinic will talk to you about whether the embryo is suitable to be transferred.
How safe is it to use frozen embryos in treatment?
It’s just as safe as using fresh embryos in treatment. The main risk is having a multiple birth (twins or triplets), which can pose serious health risks to both mum and babies. You can reduce your risk of having a multiple birth by transferring only one embryo to the womb, a process known as elective single embryo transfer or eSET.
Find out more about embryo transfer
Find out more about the risks of multiple births
Clinics are required to offer counselling to all patients undergoing this process – it can be particularly helpful at this time.
What if I don’t use all my embryos during my treatment?
You can either dispose them or donate them (to someone else or for use in research or training). In both cases, you and your partner/donor will need to give your consent in writing, your clinic should provide the relevant forms.
Donate them to someone else: Give someone the most precious gift of all by donating your embryos to someone in need.
Find out more about donating your embryos
Donate them to research: Research on eggs, sperm and embryos is invaluable in helping scientists to understand causes of infertility and develop new treatments.
Find out more about donating to research
Donate them to training: Trainee embryologists need embryos to practice techniques, such as removing cells from embryos and mastering the freezing/thawing process.
Dispose them: Some people prefer to dispose of their embryos. Embryos that are no longer needed are simply removed from the freezer and allowed to perish naturally in warmer temperatures or water
From our partners
Freezing of gametes and embryos (British Fertility Society)
Support for anyone struggling to conceive (Fertility Network UK)
Review date: 6 November 2025
