BLOG | NEWS

Why a higher IVF success rate may not mean a better chance

27 Oct 2026

By ProFertility

Two women smiling and talking while walking through a park in coats and scarves

A higher advertised IVF success rate does not automatically mean a better chance for you. The figures may count different outcomes, start at different treatment stages or describe different patients. The first step is to find out what the percentage actually measures.

Here is a useful way to read a fertility headline: write the words after “per” before comparing the number in front of it. Our guide to understanding IVF success rates gives you a practical comparison sheet and explains the main measures.

The same outcomes can produce 24%, 30% and 40%

Imagine a completely fictional teaching example: 100 treatment starts lead to 80 egg collections and 60 embryo transfer procedures. Each transfer uses exactly one embryo. Within the defined follow-up, 24 birth events are recorded. There are no further transfers in this simplified example.

Divide 24 by 100 and the result is 24% per treatment start. Divide it by 80 and it becomes 30% per egg collection. Divide by 60 and it becomes 40% per transfer procedure. Because every transfer used one embryo here, it is also 40% per embryo transferred.

Those figures describe the same invented pathway. The larger percentage has not created additional births: counting began later. These are arithmetic examples, not UK averages, clinic results or predictions.

Which stage are you deciding about?

If you already have an embryo ready for transfer, a transfer-based figure can address part of the discussion. If you are deciding whether to start ovarian stimulation, you also need to understand the possibility of not reaching collection or transfer. Your decision begins earlier than the headline's denominator.

This is a useful distinction for people with previous low response or embryo-development difficulties, and for anyone working out what an entire treatment attempt might involve. It applies across own-egg, donor and solo or LGBTQ+ routes, but the relevant comparison group changes with that route.

“Per transfer” and “per embryo transferred” are different

A transfer procedure can involve more than one embryo. Counting the procedures is therefore different from counting the embryos. In our fictional example they matched only because we deliberately specified one embryo each time.

Do not shorten a label until its meaning changes. When someone shares a screenshot, retain the full heading, age group, treatment type and date. Otherwise a useful piece of information can become a misleading comparison without anybody intending to mislead.

The debate is about which question deserves the headline

The HFEA's December 2025 report on its clinic-statistics consultation records different priorities among response groups. Patients preferred a measure beginning at cycle start; professionals preferred births per embryo transferred. The consultation is evidence about preferences in that exercise, not evidence that either measure improves treatment outcomes.

Both perspectives reveal something useful. Readers committing money, time and physical effort want to understand the journey they may begin. A later-stage measure describes outcomes after reaching a particular point. A responsible explanation should help readers move between those views rather than force one percentage to answer every question.

A selected group is not everyone who started

Consider a result reported after transfer of an embryo selected through PGT-A. That figure starts after egg collection, fertilisation, development and testing. It does not tell you how many people beginning the pathway had no embryo available to transfer.

The HFEA's current PGT-A information separates effects on miscarriage from effects on having a baby and discusses the possibility of fewer embryos remaining for transfer. A persuasive selected-transfer percentage is not, by itself, proof that adding the test improves the overall chance of a baby. The relevant evidence needs the appropriate starting group and endpoint.

Your comparison needs the rest of the sentence

“A birth in which group, counted from which stage, over what period?” is a more useful comparison than a league table of percentages. Ask whether eggs are the patient's own or donated, which age is used, whether frozen transfers are included and how incomplete follow-up is handled.

Then put uncertainty beside the number. A small dataset can move markedly after a few outcomes. The HFEA publishes reliability ranges for clinic figures; these are part of the information, not decoration around an otherwise exact ranking.

Keep the treatment plan larger than the percentage

Once the numbers are comparable, include the things that will shape everyday care: monitoring access, short-notice appointments, communication, counselling, safety and the total written quote. A clinic that fits a work pattern, disability or travel requirement may make a practical difference that a headline never measures.

ProFertility's approach is to connect evidence with the actual decision. Understanding a denominator is not a statistics exam. It helps you see which part of the proposed journey a claim covers and what still needs explaining before you commit.

Build your comparison: use the IVF success-rates Library guide alongside our Complete Guide to IVF. Keep the definitions with the figures, then discuss the parts that matter for your own route.