Using Your Eggs: A Guide to Egg Thawing

What actually happens when you decide to use your frozen eggs

If you've frozen your eggs and are starting to think about using them, you've already lived with a lot of uncertainty. Now you're stepping into another stage: thawing. It's the bit no one really talks about at the start, but it matters because not every egg that goes into the freezer comes out the other side ready to be fertilised.

This guide walks you through what happens during egg thawing, why some eggs survive and others don't, what influences the odds in your favour, and the questions worth asking your clinic before you start. 

The honest headline: thaw survival rates have improved dramatically over the last decade thanks to a freezing technique called vitrification. But outcomes still vary, between individuals, between clinics, and between eggs frozen years apart. Knowing what to expect helps you make informed choices.

What actually happens during the thawing process

When you decide to use your frozen eggs, your clinic's embryology team will warm them in a carefully controlled lab process. It's quick usually a matter of minutes per egg but it's also delicate.

Your eggs were frozen using a technique called vitrification, which means they were cooled extremely fast in liquid nitrogen at minus 196°C. Thawing reverses that process. The egg is rapidly warmed and the cryoprotectant chemicals that were used to protect it during freezing are gradually washed out. The embryologist then checks each egg under a microscope. Some eggs survive looking healthy and intact. Others don't, they may show damage to the outer membrane or internal structures, and they cannot be used.

Only eggs that survive thawing move on to the next stage: fertilisation, almost always with a technique called ICSI (intracytoplasmic sperm injection), where a single sperm is injected directly into each egg.

This whole stage usually happens on a single day, and you may not even be in the clinic when it occurs.

Why some eggs survive thawing and others do not

Egg thaw survival isn't random, but it isn't fully predictable either. A few things shape the odds.

Egg quality at the time of freezing

Eggs are at their most resilient when they were frozen at a younger age. Younger eggs tend to have stronger structural integrity and fewer chromosomal issues, which means they handle the freeze-and-thaw process better. In a 2023 UK cohort study at Guy's Hospital in London (one of the largest UK datasets so far), the average egg survival rate after thaw was around 74%. Survival was higher for eggs frozen at younger ages.

The freezing technique used

Vitrification has substantially improved survival rates compared to older slow-freezing methods. If you froze your eggs in the UK in the last decade, they were almost certainly vitrified. Older eggs frozen using slow-freezing typically have lower survival rates.

Lab and embryologist experience

Thaw survival is sensitive to small details: timing, temperature, the skill of the embryologist. Clinics that thaw a lot of eggs each year tend to develop more consistent results. The HFEA notes that outcomes vary with clinics' experience and practitioners' skills. A clinic that has been doing vitrification routinely for many years, and that thaws a meaningful volume of eggs each year, is generally a safer bet than one that does it rarely

How long the eggs were stored

Current evidence suggests that storage time itself does not significantly affect egg quality once eggs are properly vitrified — they are held in liquid nitrogen at minus 196°C, where biological activity essentially stops. The HFEA confirms there is no evidence that long storage harms eggs.

What thaw survival statistics actually mean

When clinics quote a 'thaw survival rate', they usually mean the percentage of eggs that come out of the freezer looking intact and viable enough to attempt fertilisation. It is not the same as your chance of having a baby.

Here's a more honest way to think about it. From the moment you froze your eggs, you face a chain of probabilities:

• Eggs that survive thawing

• Surviving eggs that fertilise successfully

• Fertilised eggs that develop into healthy embryos

• Embryos that lead to a pregnancy when transferred

• Pregnancies that result in a live birth

Each step has its own attrition. In the Guy's Hospital UK cohort, around 74% of eggs survived thaw, around 67% of those fertilised, and around 35% of embryo transfers led to a live birth. None of these numbers stand alone, they multiply through the chain.

That's why a clinic quoting an 80% thaw survival rate isn't promising you an 80% chance of a baby. It's telling you about one stage of a much longer process.

Questions to ask your clinic

If you're approaching thaw, the conversation with your clinic is one of the most useful you can have. These questions are worth bringing along:

• How many egg thawing cycles does your clinic perform each year?

• What is your clinic's average thaw survival rate, and how is it calculated?

• What is your fertilisation rate after thaw using ICSI?

• How many eggs of mine do you recommend thawing in the first attempt?

• If too few eggs survive, what happens next? and at what cost?

• What proportion of patients my age have had a live birth from their stored eggs at this clinic?

• Is the team thawing my eggs the same one that froze them, or a different lab?

The HFEA publishes the success rates of every UK-licensed clinic, broken down by age and treatment type, and it's worth comparing the numbers a clinic gives you with what's published.

What if my eggs don't survive thawing?

It happens, and it can be devastating. If your eggs don't survive in the numbers you hoped for, you have a few possible paths:

• Thaw additional eggs — if you have more in storage.

• Consider an IVF cycleusing fresh eggs — depending on your age and ovarian reserve.

• Explore donor eggs — younger donor eggs have higher success rates and can be a meaningful path to parenthood.

• Take time to grieve — this isn't just a medical setback; it can be a profound emotional one. Specialist fertility counsellors can help.

Practical takeaways: what should you do next?

• Get clear on your numbers — how many eggs you froze, at what age, and using which freezing technique.

• Look at HFEA clinic data — see how your clinic compares with national averages on storage and treatment outcomes.

• Ask the right questions — use the list above when you have your pre-thaw consultation.

• Plan for emotional support — whether that's a partner, friend, therapist, or fertility counsellor. This stage often surprises people with how much it brings up.

Take the next step with us

Whatever stage you are at, you don't have to figure this out alone. At Egg Advisor we are independent — we don't sell treatment, and we don't take referral fees from clinics. We help you understand your numbers, your options, and your feelings.

• Book a one-to-one appointment with an Egg Advisor for personalised guidance.

• Speak to an Egg Therapist if the emotional side feels heavy right now.

A note from Egg Advisor

Egg Advisor is independent. We share recommendations based on experience, current knowledge and professional practice and are not accountable for service provision from other providers. This article reflects UK data and regulation at the time of writing. If your situation changes, please consider booking an appointment with an Egg Advisor for personalised guidance.