June 6, 2023
7 minutes

How Successful Is Egg Freezing? And Which Clinic Has the Best Success Rates?

How Successful Is Egg Freezing? And Which Clinic Has the Best Success Rates?

In an eggshell...

  • As of 2016, 18% of frozen egg fertilisation cycles were successful
  • Egg-freezing data in the UK is regulated and provided by the HFEA
  • Age at freezing is the key factor affecting success rates. Apart from that, your ovarian reserve, response to medication, health conditions, lifestyle factors, and number of eggs frozen play a role
  • Success rate definitions vary between clinics- but asking the right questions can help your journey

Success rates, and with egg freezing?

Surprisingly, yes. It’s a parameter that’s influenced by a lot of factors. Basically your age, the clinic chosen, and the treatment protocol all play a key role in how successful your egg-freezing cycle can be. 

And by that we mean, how successfully they’re frozen, warmed, or their outcomes with self or donor IVF. 

So regardless of the reason behind your egg-freezing journey, the question really boils down to this: What’s the success rate for my egg-freezing cycle, and will it result in a healthy pregnancy when I’m ready to use them?

Let’s do a deeper dive into what factors affect your egg-freezing cycles, how clinics calculate success rates, and what this means for you. 

What Is an Egg Freezing Success Rate?

Different definitions of success rates are used for different stages of the egg-freezing cycle, which can be confusing. Let’s find out more about each.

  • Egg retrieval rate: This is the percentage of women who have at least one mature egg retrieved during the egg-freezing process.
  • Egg fertilisation rate: This is the percentage of eggs that are fertilised with sperm, and form a zygote (a fertilised egg) after being retrieved.
  • Embryo development rate: This is the percentage of fertilised eggs that develop into embryos (aka, the phase where your future baby is still a bunch of cells).
  • Implantation rate: This is the percentage of embryos that implant in the uterus after being transferred.
  • Live birth rate: This is the most common way to calculate egg-freezing success rates. It is calculated by dividing the number of live births (or babies carried to full term) by the number of eggs frozen.

You’ll see live birth rates used regularly as this is the end goal most women are thinking of. But it doesn’t always paint the whole picture. The steps in between, also add up to the final stage, making them just as important.

Also check: Amilis's egg freezing success rates calculator

Which Factors Can Affect Egg Freezing Success Rates?

Several factors can impact the outcomes of egg freezing (and, ultimately, fertilisation and pregnancy). Some of these include:


Age is the most significant factor influencing egg-freezing success rates. 

Older women may have eggs with less quality, as the genetic abnormalities in eggs increase with age. 

Younger women tend to have higher-quality eggs, which have a better chance of surviving the freezing and thawing process. This results in more successful pregnancies.‍

Ovarian Reserve:

Ovarian reserve is the quantity and quality of a woman's remaining eggs. Fertility tests such as Anti Mullerian Hormone and Antral Follicle Count can provide an insight into your ovarian reserve. 

Women with a higher ovarian reserve usually have larger numbers of viable eggs available. Especially at younger ages, since the quality is higher, there is a chance of freezing more number of good quality eggs. 

Also read: What your AMH levels can tell you about your egg-freezing journey

Medical history and health conditions:

Health conditions, such as genetic disorders and autoimmune diseases, can impact egg quality and fertility. 

Whilst conditions like polycystic ovary syndrome (PCOS) or endometriosis can affect egg freezing success rates, egg freezing is often still an effective fertility treatment for these women.

Also read: Can I freeze my eggs if I have PCOS?

Response to Ovarian Stimulation:

Before egg freezing, you are put on ovarian stimulation protocols to help increase the egg growth for the month. 

Growth-inducing hormones such as FSH and LH are injected to stimulate the ovaries to produce multiple eggs. However, there’s no “one protocol fits all” solution and your body’s response to stimulation may vary. 

In some cases, if your response is lower than expected, there are genetic or blood tests conducted to figure out the cause and personalise the protocol for you accordingly.

Freezing Method:

The method used for freezing eggs can also affect success rates. Earlier, a slow freezing method was used for preservation, which had lower success rates. 

However, most clinics now have adopted an updated method, Vitrification, or rapid freezing technique, which has better success rates than the previous method.

Clinic Expertise and Laboratory Techniques:

The experience and expertise of the fertility clinic and its laboratory staff play a crucial role in determining success rates. 

Skilled professionals and state-of-the-art laboratory techniques can improve the handling, freezing, and thawing processes, increasing the chances of success.

Lifestyle factors:

Factors like smoking, excessive alcohol consumption, and obesity can negatively impact egg quality and overall fertility. This is reflected in success rates.

Additionally, stress can impact fertility and egg freezing. Bodily changes associated with stress, including the production of cortisol, are linked to reduced egg quality and lower pregnancy rates.

Number of Eggs Frozen:

It’s a fine balance between the number of stimulation cycles, and collecting enough eggs. You may start out with 12 follicles and end up with 7-8 eggs, with 5-6 fertilised. 

Hence, egg-freezing cycles aim to increase the number of mature eggs collected. Women below 38 usually have 7-14 eggs collected, but the number varies from clinic to clinic.

Also read: Wondering why your follicles and egg yield may not match? Read all about it at Amilis! 

While these factors can affect success rates, everyone’s situation is unique. A fertility specialist can provide personalized guidance and help assess the likelihood of success based on individual circumstances. 

If you have questions about struggling to choose a fertility specialist, Amilis can help you explore your options.

Are Egg Freezing Success Rates Improving?

Egg-freezing success rates have been improving in recent years. The most recent Human Fertilisation and Embryology Authority (HFEA) figures from 2016 suggest 18% of cycles where a woman’s own frozen egg was fertilised resulted in a live birth. For donor eggs, the percentage stands at 30%

This is largely due to the development of new technologies, such as vitrification. Vitrification offers higher survival rates and better chances of successful pregnancy.

 Compared to its previous counterpart, the slow freezing method. 

Additionally, clinics now have access to better equipment and resources and have standardized the procedure, leading to minimal errors.

Egg freezing success rates by age: an overview

As per the HFEA, the majority of women freezing their eggs via NHS were under 35, with almost 90% being under 38. 

However, the most common age of women freezing their eggs in the UK averages to 38. 

This emphasises the fact that knowing about your success rates by age can significantly help you boost your egg-freezing success rates and your future chances at a healthy pregnancy! 

But if we were to look at egg freezing success rates by age, this is how it would look like:


Number of eggs

Live birth rate

Below 35






Above 40



As per statistics, a woman below 35 years of age would need around 15 eggs for a 80% chance at a live birth rate or a successful pregnancy. And as per the table, the statistics reduce for women older than 35 and 40. 

And as age increases, the number of eggs needed for a better success rate also increases, indicating the need for multiple egg freezing cycles.

What are egg-freezing success rates like for women above 35?

As mentioned above, age is the most important factor affecting egg-freezing success rates. Women who freeze their eggs before the age of 35 have a much higher chance of success. 

Interestingly, when you freeze your eggs matters more, compared to when you use them

This is because the number and quality of eggs decline with age: women who freeze their eggs before 35 have more eggs of better quality.

However, the average age of a woman who freezes her eggs in the UK is 38. This means data on egg freezing success rates mostly represents women over 35: above the age of peak success.

The HFEA advises women to use the IVF success rates for women in their age group (using fresh eggs), rather than egg freezing success rates. This data is likely to better represent the live birth rate from frozen egg fertilisation, especially in women below 35.

IVF birth rates by age group spanning from 1991 - 2019. Source: HFEA, 2019

How are Egg Freezing Success Rates calculated in the UK?

In the UK, the HFEA (Human Fertilisation And Embryology Authority) regulates the practice of egg freezing. The HFEA sets standards for fertility clinics and makes sure that:

  • Patients are given accurate information about the risks and benefits of egg freezing
  • Patients are treated safely and ethically
  • Patients can make informed decisions about egg freezing
  • Clinics provide high-quality care
  • Clinics keep records of all egg-freezing procedures

The HFEA requires fertility clinics to publish their success rates, but they don't regulate how those rates are calculated. Plus success rates may vary based on the number of cases a clinic has. 

The verdict? 🧑⚖️

Well, we recommend still sticking to the figures rather than anything else, as technically, they still represent statistics around egg freezing.

How Do Egg Freezing Success Rates Vary Between Clinics?

As clinics calculate success rates differently, it can be difficult to compare.

For example, some clinics might only count the number of live births per egg retrieval. Others might count the number of live births per cycle. And some clinics might only count the number of live births for women under 35, while others might include women of all ages.

Success rates can vary due to different patient selection, techniques, medical expertise, and the clinic's overall experience in performing egg-freezing procedures.

So, what's a girl to do?

Let’s talk about what you can ask to understand how successful a clinic really is.

What Can I Ask a Fertility Clinic About Their Success Rates?

You're about to make a big decision that could impact your future, so it's important to get all the information you can before you choose a clinic for your egg-freezing journey.

That includes asking specific questions about the clinic's success rates.

These can include:

  • What is your success rate for women who freeze their eggs before the age of 35? And after?
  • Can you provide information on the success rates for women of my age group?
  • How do you calculate your success rates?
  • What is your clinic's success rate for live births per X number of eggs frozen/thawed?
  • How does your clinic's success rate compare to national averages or benchmarks?
  • Are there any additional factors that may impact success rates in my case?

In the end, all you’re trying to get is the information that will benefit your journey. Ideally, the more insights, the better informed you will be to make decisions with your healthcare provider. 

A Final Note from Amilis

Choosing a fertility clinic can be like comparing apples to oranges. There are so many factors that come into play, such as the distance, the team, and your experience, and one of the most crucial ones happens to be success rates. 

Remember, it's okay (and necessary) to ask your clinic about their success rate, and any other questions that you may have about the process. 

You can even start with our clinic comparator to assess clinics nearby. With Amilis, you not only get discounted rates on your tests and egg-freezing cycles and appointments but you get a stellar team (that's us 👋) supporting you with every step! 

Still unsure on how to choose or wondering if egg freezing is right for you? don’t worry, we can help - take our quiz to get started.

Deciding if egg freezing is for you?
Well you don't have to contemplate alone. Amilis can help you make the decision with clear, personalised, empathetic advice.
Book a call
Deciding if egg freezing is for you?
Well you don't have to contemplate alone. Amilis can help you make the decision with clear, personalised, empathetic advice.
Book a call
Written by
Dr Zoe Miller
Medical Editor and Doctor at NHS