Egg Freezing and Fertility Preservation: What the Data Shows

The honest picture, with numbers

Egg freezing has grown faster than almost anything else in fertility medicine. HFEA data show UK egg storage cycles rising from 2,567 in 2019 to 6,932 in 2023 — a 170% increase — making up 7% of all treatment cycles. The biggest growth was among patients in their thirties: cycles at ages 30–34 rose 67% between 2022 and 2023, and at 35–37 by 53%.

Two numbers from the HFEA tell you most of what you need to know about how it is being used. The average age at freezing is 35. The average age at thawing is 40. And the number of patients who return to use their stored eggs remains low.

Success rates are where honesty matters most. The HFEA's own position is that when looking at success rates for frozen eggs, "numbers tend to be quite low" — the volume of frozen-egg thaw cycles is small compared with fresh transfers, and historical data is not comparable with current practice. Its advice is to look instead at success rates for fresh IVF cycles using your own eggs in your age band, because those figures rest on far more cycles. For 2023 those were around 35% birth rate per embryo transferred at 18–34, falling to 5% at 43–44 using a patient's own eggs. Across frozen embryo transfers generally, the 2023 average was a 39% pregnancy rate and a 33% birth rate per embryo transferred — and the HFEA notes that outcomes are largely related to the patient's age at egg collection rather than at transfer.

That last clause is the whole argument for freezing earlier rather than later, and also the reason a cycle at 39 buys less than the marketing implies. The HFEA is explicit that egg freezing should not be treated as an insurance policy.

What actually affects it

Age at freezing, above everything

Because outcomes track the age of the egg rather than the age at transfer, the year you freeze matters more than any other variable. HFEA data show birth rates per embryo transferred above 25% for women under 35, dropping to 15% or lower over 40 and under 5% over 44. Freezing at 32 and thawing at 40 is a different proposition from freezing at 39 and thawing at 42, even though both feel like "freezing in advance".

How many eggs you get

One cycle produces a variable number of mature eggs, and not every egg survives thawing, fertilises, or becomes a transferable embryo. This attrition is why clinics often discuss more than one collection cycle. Ask your clinic for its own thaw survival and fertilisation rates rather than accepting a national average.

Freezing method

The HFEA notes that vitrification — fast freezing — has proved more successful than the older slow-cooling method. This is one reason older outcome data understates what current practice achieves, and one reason to ask which method a clinic uses.

The risks

The collection itself is an IVF cycle: two to three weeks of hormone medication, then egg collection under anaesthesia. The principal risk is ovarian hyperstimulation syndrome, which the HFEA describes as potentially fatal in its severe form. It is uncommon and monitored for, but it is not nothing, and it is worth hearing described properly before you consent.

The legal and financial reality

Storage limits

UK law changed on 1 July 2022. Previously most people could store eggs for 10 years, with longer storage reserved for those with premature infertility or facing fertility-affecting treatment. The law now permits storage for use in treatment for any period up to a maximum of 55 years — but consent must be renewed every 10 years. If consent is not renewed, the eggs are lawfully disposed of. That renewal requirement is the practical trap: it depends on the clinic being able to reach you, so keep your contact details current for decades.

Cost

The HFEA's published UK figures: around £3,350 for collection and freezing, £500–£1,500 for medication, £125–£350 a year for storage, and around £2,500 for thawing and transfer — roughly £7,000 to £8,000 in total for one cycle through to a transfer, before any repeat cycles.

Fertility preservation for medical reasons is a different pathway

If you are facing treatment likely to impair your fertility — cancer treatment being the most common example — you are in a different category with different rules. NICE NG257 recommends discussing fertility preservation with anyone preparing for such treatment, at the earliest possible opportunity where treatment is urgent. It recommends offering oocyte or embryo cryopreservation to women and girls of reproductive age in that position, and sperm cryopreservation to men and boys, with ovarian tissue cryopreservation considered where oocyte or embryo freezing is not feasible, such as before puberty.

Two NICE recommendations here are worth quoting to anyone who tells you otherwise. First: for NHS-funded fertility preservation, do not apply the eligibility criteria used for conventional fertility treatment, including the lower age limit. Second: organise follow-up at least every 5 years, and continue NHS-funded storage for people who remain at significant risk of infertility. NICE also says to be clear up front that the usual eligibility criteria will apply when it comes to using the stored material.

NICE further recommends expediting fertility specialist referral where planned treatment may cause infertility. If you have a cancer diagnosis and nobody has raised fertility with you, raise it yourself, immediately — the window is often days, not months.

What to do next

1. Ask the clinic for its own numbers, not national ones: eggs collected per cycle at your age, thaw survival rate, fertilisation rate, and live births from thawed eggs. Ask how many patients have actually returned to use eggs frozen there.
2. Ask what a realistic total cost looks like including a second cycle, ten years of storage and a thaw-and-transfer. Compare that to the single headline price.
3. Diarise your consent renewal. Every 10 years, and keep the clinic's records of your address and email current.
4. If this is for medical reasons, say so explicitly and ask for the fertility preservation pathway. Different criteria apply, and NICE says the usual age and eligibility limits should not be used.
5. Ask what happens to the eggs if you die, if the clinic closes, or if you want them moved. Get it in writing.

When to seek help

If your reason for considering egg freezing is that you are worried about your fertility right now, that is a reason for assessment rather than storage. NICE recommends referral at first presentation if you are 36 or over, or if either partner has a known or suspected cause of infertility. NICE also states that AMH should not be used to predict your chance of conceiving naturally — it predicts ovarian response to stimulation, which is genuinely useful for planning an egg freezing cycle, and genuinely misleading if read as a verdict on your fertility.