Treatment Essentials: Embryo Freezing
Embryo freezing — also known as embryo cryopreservation — is a well-established fertility preservation technique that allows you to freeze and store embryos for potential future use, whether you’re preparing for later pregnancy, planning for a sibling, or safeguarding your fertility ahead of medical treatment. This guide breaks down what embryo freezing involves, who it’s for, how it works, and what to consider before getting started.
Author
Tassia O’Callaghan
Reviewed by
Kayleigh Hartigan
19 min read
Updated 12th August 2025
Treatment Spotlight:
- Embryo freezing (cryopreservation) is the process of freezing and storing embryos for future fertility treatments like IVF, offering a widely used option for fertility preservation or family building.
- A “freeze-all” cycle is when all embryos from an IVF cycle are frozen instead of transferring fresh. This might be recommended for medical reasons — like reducing the risk of OHSS — or to give the body time to recover before transfer. In some cases, clinics don’t charge extra for this if it’s a clinical decision. [1]
- It’s often chosen by people with extra embryos after a fresh IVF cycle, those delaying pregnancy using embryos created with a partner or donor, or individuals facing medical treatments that threaten fertility.
- The process involves hormone stimulation, egg retrieval, fertilisation, and freezing only high-quality embryos using modern vitrification techniques, which offer around a 90% survival rate after thawing. [2]
- Success rates depend on factors like age at freezing, embryo quality, and clinic expertise, with frozen embryo transfers (FET) now achieving pregnancy and live birth rates similar to — or sometimes better than — fresh transfers. [3]
- Emotional, legal, and financial considerations are part of the journey, including making decisions about storage, future use, and coping with the possibility that not all embryos will survive or lead to pregnancy.
- A freeze-all cycle is when all embryos from an IVF cycle are frozen (rather than transferring fresh), often used to improve implantation conditions or reduce the risk of ovarian hyperstimulation syndrome (OHSS). [4]
What is embryo freezing?
Embryo freezing — sometimes called embryo cryopreservation — is the process of freezing and storing embryos for potential use in future fertility treatments like IVF. It’s one of the most widely used fertility preservation methods today and can be an important part of your fertility path, whether you’re actively trying to build your family now or planning ahead for later.
After an IVF (in vitro fertilisation) or ICSI (intracytoplasmic sperm injection) cycle, any good-quality embryos that aren’t transferred fresh into the uterus can be frozen for later. This gives you the option to try again if the fresh cycle doesn’t result in a pregnancy or to come back later for a sibling journey — without going through another full egg collection cycle. For some people, embryo freezing is also part of fertility preservation ahead of medical treatments like chemotherapy, or before gender-affirming procedures.
The science behind freezing has advanced significantly. Clinics now use a technique called vitrification (fast freezing), which dramatically reduces the formation of ice crystals that can damage cells. This is much safer and more effective than the previous slow freezing methods, which relied on a gradual temperature drop. With vitrification, survival rates after thawing are much higher — giving frozen embryos an excellent chance of leading to a healthy pregnancy when they’re eventually used. [5,6,7]
Treatment Essentials: IVF
Curious about IVF and how it all fits together? From the early steps to embryo transfer, our in-depth guide breaks down the process, potential risks, and what to expect.
Who is embryo freezing for?
Embryo freezing can be an option for a wide range of people navigating fertility treatment — it’s often considered when:
- You’re going through IVF or ICSI and have extra embryos left after a fresh transfer. Instead of discarding them, you can freeze those good-quality embryos for future use — whether you’re planning another transfer soon or want to try for a sibling down the line.
- You’re planning ahead and want to preserve your future chances of pregnancy. This might be because you’re delaying parenthood for personal, career, or relationship reasons but already have embryos created with a partner or donor. Freezing them now helps protect your options for when the time feels right.
- You’re facing medical treatments or conditions that could impact your fertility. If you’ve been diagnosed with cancer, are preparing for chemotherapy, or need surgery on reproductive organs, embryo freezing (sometimes alongside egg or sperm freezing) can help safeguard your fertility for the future.
Embryo freezing requires both eggs and sperm, so it’s a route often taken by couples or individuals using a sperm donor, rather than people freezing their eggs on their own. If you’re unsure which option is right for you, your clinic can guide you through the pros and cons based on your situation and goals. [5]
Before you start embryo freezing, remember:
Before you begin the embryo freezing process, it helps to understand what’s involved — practically, physically, and emotionally. Here’s what to keep in mind:
- You can’t freeze an embryo without fertilisation. Embryo freezing always requires both eggs and sperm — whether from a partner or a donor. If you’re considering freezing but aren’t ready or able to use sperm right now, egg freezing might be a better fit.
- Embryo freezing is not a guarantee of future pregnancy. While success rates with frozen embryo transfers (FET) have improved dramatically in recent years, outcomes depend on many factors, including embryo quality, your age at freezing, and your overall reproductive health. [8,9]
- You’ll need to make important decisions about storage and future use. Freezing embryos comes with legal and emotional considerations, such as how long you want to store them, what happens if you or your partner change your mind, and whether you might want to donate unused embryos to research or another family.
- It’s a physically and emotionally demanding process. Embryo freezing isn’t just a lab procedure — it involves the same hormone stimulation and egg retrieval process as IVF, which can bring physical side effects (like bloating, mood swings, or fatigue) and emotional ups and downs. Having support in place — from a partner, friend, counsellor, or community — can really help.
- Some clinics offer multi-cycle packages — where you go through several rounds of stimulation and egg collection in close succession to maximise the number of embryos created and frozen. If you’re doing a freeze-all cycle, your clinic might also recommend a higher stimulation dose, since there’s no fresh transfer that cycle and your body has time to recover before the next step. This approach can be especially useful if you’re trying to bank embryos quickly, or if time is a key factor in your treatment plan.
- Not all embryos will be suitable for freezing. Only embryos that meet certain quality standards are frozen; others may not survive the freezing and thawing process. It’s important to go in with realistic expectations and have open conversations with your clinic about grading and outcomes.
- Legal consent is essential. You (and your partner, if applicable) will need to give written consent for embryo storage, specifying how long they can be stored (currently up to 55 years in the UK) and what should happen if either of you withdraws consent. Keeping your clinic updated if your circumstances or wishes change is key. [10]
- Some people explore freezing both eggs and embryos. Depending on your situation, you might want to preserve maximum flexibility by freezing both fertilised (embryos) and unfertilised (eggs) — especially if you want to keep options open for use without partner or donor consent later.
- Costs can add up — now and later. It’s not just the upfront cost of the IVF cycle and freezing that matters; you’ll also need to factor in annual storage fees and the cost of any future transfer cycles. It’s worth asking your clinic for a clear, upfront breakdown of these expenses so you can plan ahead confidently.
How to Choose the Best Fertility Clinic
Choosing a fertility clinic is a big decision — and we’ve made it clearer. Our guide walks you through what to look for, what to ask, and how to feel confident in your shortlist.
Embryo freezing: step-by-step
From your first consultation to the moment your embryos are stored, here’s what the embryo freezing journey typically looks like, step by step.
Step 1: Pre-treatment
Time: Around 2 weeks
Location: Clinic
Before starting, your clinic will run a set of pre-treatment tests — often called a fertility MOT — to understand your ovarian reserve (the number and quality of eggs available). This helps tailor your treatment plan for the best possible outcome.
Tests include:
- Blood tests for AMH (Anti-Müllerian Hormone) and FSH (Follicle Stimulating Hormone) to estimate egg quantity.
- A pelvic ultrasound (Antral Follicle Count) to check the number of immature follicles that could mature into eggs during the cycle.
- Screening for infectious diseases, like Hepatitis B and C, as a legal requirement before embryo freezing. [11]
After these results, you’ll have a consultation to review your personalised treatment plan, and a nurse will show you how to give yourself the hormone injections at home.
Step 2: Ovarian stimulation
Time: 2–4 weeks
Location: Home, with in-clinic monitoring
Here, you’ll start hormone injections, usually on day 1 or 2 of your period, to stimulate your ovaries to grow multiple eggs — not just the single egg you’d release in a natural cycle.
You’ll need regular monitoring with ultrasound scans and blood tests to check follicle development. If your protocol includes a down-regulation phase, you may take additional medications before starting stimulation.
Step 3: Trigger shot and egg retrieval
Time: 36 hours
Location: Home and clinic
Once your follicles are ready, you’ll take a trigger shot — an injection of hCG that matures the eggs and prepares them for collection.
About 36 hours later, you’ll have a minor surgical procedure at the clinic to retrieve your eggs. This takes around 15–30 minutes under sedation. Afterwards, your doctor will tell you how many eggs were collected and whether further cycles might be recommended.
Step 4: Fertilisation and embryo development
Time: 3–6 days
Location: Lab
In the lab, your collected eggs are fertilised with sperm from your partner or donor. Over the next few days, the embryologists monitor how they develop, looking for healthy cell division and growth.
Step 5: Embryo grading, freezing, and onward storage
Time: Day 3 or Day 5–6
Location: Lab
Not every embryo will be frozen — only those that meet specific quality standards. Embryos are graded based on their development stage, symmetry, and cell quality. Those that are suitable are frozen using vitrification, a fast-freezing technique that helps protect delicate cells from ice damage. They’ll then be stored securely in liquid nitrogen until you’re ready to use them.
How long does embryo freezing take?
The embryo freezing process usually takes around 4–6 weeks from your first appointment to the point when your embryos are frozen and safely stored.
That’s 2–4 weeks for ovarian stimulation and monitoring, a few days for egg retrieval, fertilisation, and embryo development, and up to a week for embryo grading and vitrification (fast-freezing).
If you include time for recovery, emotional processing, or planning your next steps after freezing, it’s worth adding another couple of weeks — especially if you’re deciding when (or whether) to move on to a frozen embryo transfer (FET) or to take a break before continuing treatment.
Understanding embryo freezing success rates
Success rates after embryo freezing depend on several key factors:
- Embryo quality at the time of freezing
- Your age when the embryos were created and frozen
- The experience and skill of the clinic managing your treatment
Thanks to improvements in lab techniques, particularly the use of vitrification (fast freezing), frozen embryo transfer (FET) cycles now often have pregnancy and live birth rates comparable to — or sometimes even higher than — fresh embryo transfers. This is partly because the uterine environment in a frozen cycle can be better prepared for implantation, without the hormonal effects of ovarian stimulation.
Recent UK data shows that the average pregnancy rate per frozen embryo transferred is around 36%, and the average live birth rate per frozen embryo transferred is about 30%. [3]
This puts FET success rates on par with, and in some cases slightly better than, fresh transfer rates — especially when the uterine lining can be optimally prepared in a frozen cycle.
Keep in mind: these are averages. Your personal chance of success will reflect your individual circumstances, including your age at the time of freezing and the number and quality of embryos available.
Embryo survival during freezing and thawing
With modern vitrification (fast freezing), most embryos tolerate the freeze–thaw process very well. Current data shows survival rates of around 90%, meaning the majority of embryos remain viable after thawing. However, in some cases, certain cells or even entire blastocysts may not survive — this is unpredictable and can vary from patient to patient. [2]
What happens after embryo freezing?
Some people store their embryos for just a few months before planning a frozen embryo transfer (FET), while others keep them in storage for years before deciding if, when, and how to use them. Depending on your situation, you might consider using your frozen embryos in a future FET cycle, as part of a surrogacy arrangement, or alongside donor options.
It’s not just about the medical next steps — there are emotional and legal aspects to think through too. You’ll need to make decisions about long-term storage, renewal of consent, and what happens if life circumstances change (for example, a relationship change or a shift in family plans). For many, this phase can bring up big feelings: hope, uncertainty, and even grief if the path hasn’t gone as expected.
What are the risks of embryo freezing?
Like any fertility treatment, embryo freezing comes with some risks:
- Ovarian hyperstimulation syndrome (OHSS): This can happen when the ovaries over-respond to the stimulation medication used to mature eggs. Most cases are mild, but severe OHSS is rare and can cause bloating, pain, or more serious complications that might need medical care. [4]
- Surgical risk: Egg retrieval is a minor surgical procedure, but as with any surgery, there’s a small risk of infection, bleeding, or complications from sedation. Your clinic will talk you through how they manage these risks and what signs to watch for. [12]
- Not all embryos survive thawing: Even with modern freezing techniques, some embryos may not make it through the thawing process when you’re ready to use them. It can be emotionally tough to navigate, so it’s worth preparing for this possibility. [2]
- Emotional and financial strain: Embryo freezing can be a hopeful, empowering choice — but it can also bring stress, both emotionally and financially. Costs can add up over time, and decision-making around storage, use, or donation can feel heavy.
- Uncertainty of outcomes: Even with excellent-quality frozen embryos, there’s no guaranteed pregnancy. Success depends on many factors, and the waiting (and wondering) can take a toll.
Is embryo freezing available on the NHS?
In some cases, yes — but access is limited.
Access to NHS-funded embryo freezing depends on where you live and your individual circumstances. Funding decisions are made by your local Integrated Care Board (ICB), and the process can vary — some referrals come through a GP, others through a specialist. There’s no single, clear pathway, which can make navigating access feel confusing. If you’re unsure, you can speak to your GP or specialist, or write directly to your ICB to ask about your options.
The NHS may cover embryo freezing if you’re facing medical treatments (like chemotherapy) or have a medical condition that puts your fertility at risk. This is part of fertility preservation care, designed to give you the option of having children later on when treatment or illness might otherwise reduce that chance. [6]
However, elective embryo freezing — for example, freezing embryos with a partner or donor to delay pregnancy for personal reasons — isn’t funded by the NHS. In these cases, most people pay privately for the IVF cycle, freezing, and storage.
Even if you’re eligible for NHS-funded embryo freezing, it’s important to check how long that funding covers storage. Some people find that while the initial freezing is funded, they need to cover the costs of extended storage after a set number of years. Always clarify the details with your clinic, so you can plan ahead with confidence.
Your NHS Eligibility
Not sure where you stand with NHS IVF funding? Let our calculator do the work and get a personalised answer in seconds.
How much does embryo freezing cost?
Embryo freezing usually costs a similar amount to IVF, as it involves the same hormone stimulation, egg collection and fertilisation process. In 2023, the median advertised cost of an embryo freezing cycle was £4,579.50. Some clinics offer “freeze-all” cycles at a slightly higher upfront price, but often include the first year of storage in that fee. For example, IVF London charges £3,900 for a standard IVF cycle and £4,600 for a freeze-all cycle with a year of cryopreservation included.
If you’re freezing surplus embryos after a fresh transfer, you’ll typically pay around £650 for freezing and one year of storage. And in cases where embryo freezing is recommended for medical reasons, such as to lower the risk of OHSS (Ovarian Hyperstimulation Syndrome), some clinics will cover the cost of freezing all embryos as part of your treatment plan.
These figures are based on advertised clinic pricing, which doesn’t always reflect the total cost patients end up paying. That’s why we’re actively analysing both clinic price lists and real-world data from our community to build a clearer picture of the true cost of embryo freezing (and other fertility treatments) in the UK.
Where can I find an embryo freezing clinic?
Finding the right clinic for embryo freezing is a big decision — and it’s about more than just proximity or price. You want a team with the expertise to handle your treatment and the compassion to make you feel genuinely supported.
You can use our Clinic Finder to browse highly rated clinics near you. If you already have an account, simply log in to keep track of your saved clinics and compare your shortlist side by side.
When exploring your options, here’s what’s worth paying attention to:
- Proven experience with embryo freezing: Ask clinics how many embryo freezing cycles they complete each year and what their outcomes look like. Familiarity with the process matters.
- Clear and upfront pricing: Get a full breakdown of what’s included in the cost — from consultations and lab work to medications, freezing, and storage — so you know exactly what you’re paying for.
- A patient-first approach: You deserve a clinic that listens carefully, takes the time to explain things, and respects your choices without pressure.
- Tailored care: The best clinics offer treatment plans designed for you — not generic, one-size-fits-all protocols. Make sure they’re considering your personal health, goals, and circumstances.
- Authentic patient reviews: Learning from others who’ve been through the process at a particular clinic can give you honest insights into the care, communication, and support you can expect.
If you’re unsure where to begin, try our Clinic Match tool — it’s designed to connect you with trusted embryo freezing providers, complete with reviews, pricing details, and expert recommendations to help guide your decision.
What if embryo freezing doesn’t work?
If embryo freezing doesn’t lead to a pregnancy, it can feel incredibly heavy — but it’s not the end of the road. There are still pathways and choices ahead, and you don’t have to face them alone.
Start by speaking with your clinic. They will discuss with you whether additional IVF cycles or any remaining frozen embryos are an option, if egg freezing or using donor eggs might offer the best chance moving forward, and any adjustments to treatment protocols that could improve outcomes in the next round, based on what you’ve already been through.
It’s also crucial to care for your emotional wellbeing. Counselling, support groups, and connecting with others who’ve walked a similar path can offer space to process grief, find reassurance, and regain a sense of hope.
Embryo freezing FAQs
What is embryo freezing?
Embryo freezing — sometimes called embryo cryopreservation — is the process of freezing and storing embryos for potential use in future fertility treatments like IVF. It’s one of the most widely used fertility preservation methods today and can be an important part of your fertility path, whether you’re actively trying to build your family now or planning ahead for later.
After an IVF (in vitro fertilisation) or ICSI (intracytoplasmic sperm injection) cycle, any good-quality embryos that aren’t transferred fresh into the uterus can be frozen for later. This gives you the option to try again if the fresh cycle doesn’t result in a pregnancy or to come back later for a sibling journey — without going through another full egg collection cycle. For some people, embryo freezing is also part of fertility preservation ahead of medical treatments like chemotherapy, or before gender-affirming procedures.
The science behind freezing has advanced significantly. Clinics now use a technique called vitrification (fast freezing), which dramatically reduces the formation of ice crystals that can damage cells. This is much safer and more effective than the previous slow freezing methods, which relied on a gradual temperature drop. With vitrification, survival rates after thawing are much higher — giving frozen embryos an excellent chance of leading to a healthy pregnancy when they’re eventually used. [5,6,7]
Sources
1. https://www.hfea.gov.uk/treatments/treatment-add-ons/elective-freeze-all-cycles/
2. https://www.cuh.nhs.uk/patient-information/embryo-cryopreservation-information-for-patients/
3. https://www.hfea.gov.uk/about-us/publications/research-and-data/fertility-treatment-2022-preliminary-trends-and-figures
4. https://www.hfea.gov.uk/treatments/explore-all-treatments/risks-of-fertility-treatment/
5. https://www.hfea.gov.uk/treatments/fertility-preservation/embryo-freezing
6. https://www.guysandstthomas.nhs.uk/health-information/fertility-preservation-for-women/freezing-eggs-or-embryos
7. https://www.newcastle-hospitals.nhs.uk/services/fertility-treatment/embryo-freezing/
8. https://rbej.biomedcentral.com/articles/10.1186/s12958-024-01210-0
9. https://pmc.ncbi.nlm.nih.gov/articles/PMC8489809/
10. https://www.hfea.gov.uk/treatments/fertility-preservation/egg-freezing/
11. https://www.hfea.gov.uk/choose-a-clinic/preparing-for-your-clinic-appointment/
12. https://www.guysandstthomas.nhs.uk/health-information/ivf-treatment/risks-ivf