IVF success rate calculator

Three different numbers all called "success rate"

Before any figure means anything, it has to be clear what it is divided by. A clinic can quote success per cycle started, per egg collection, or per embryo transferred, and the three can differ by ten percentage points or more for exactly the same treatment. Per embryo transferred is the HFEA's house measure and the one used throughout this page.

Then there is the numerator. Pregnancy rate and birth rate are not the same thing, and the gap between them is the pregnancies that do not result in a baby. The HFEA publishes both, and this tool leads with the birth rate, because that is the outcome anyone actually wants.

Age is the biggest single lever

The fall is steep and it is not gentle at any point. On fresh transfers with a patient's own eggs, the birth rate per embryo transferred runs from 35% at 34 or under, to 26% at 35 to 37, 18% at 38 to 39, 10% at 40 to 42, and 5% at 43 to 44.

That is a sevenfold difference across roughly a decade. It is the reason the HFEA repeats, in report after report, that patients should not delay contacting a GP or a fertility clinic — and it is why the average age of a first-time IVF patient passing 35 for the first time is treated as a significant finding rather than a statistical curiosity.

The age that counts is the age at egg collection, not the age at transfer. An embryo frozen at 33 and transferred at 37 carries the odds of a 33-year-old's egg, which is the whole logic behind egg and embryo storage.

Frozen transfers now beat fresh ones on the headline

The average frozen embryo transfer birth rate was 30% in 2022, against 24% for fresh. Frozen transfers have more than doubled in use over a decade while fresh transfers fell.

That comparison is less flattering than it first looks, and it is worth understanding why. Frozen transfers are often the second and third embryos from a good batch, in patients who already produced several viable embryos, and they take place in a cycle where the lining can be prepared without the hormonal aftermath of stimulation. The patients are not the same patients. Still, the shift is real enough that "freeze all" has become a routine plan rather than a fallback.

What the cumulative number does and does not tell you

Compounding a per-transfer rate across several attempts is arithmetic, not evidence. It assumes every attempt is independent, and they are not. Embryos from the same collection share the same biology. Patients who reach a third or fourth transfer are not a random sample of those who started — some stopped because treatment was working, others because it was not, and others because they ran out of money.

Treat the cumulative figure as an upper bound and as a way of seeing the shape of the odds. The honest version of the same idea is that most people who succeed with IVF do so within the first few transfers, and that each further attempt adds less than the one before.

The preliminary-data caveat is not boilerplate

The HFEA marks its 2020 to 2022 figures as preliminary and unvalidated, and explains what that means for the numbers. Birth rates normally sit about three percentage points below pregnancy rates. In the current preliminary data the gap is wider, because outcome data has not all caught up. The HFEA expects birth rates to rise once validation completes, and suggests using pregnancy rates as the better indicator of recent progress.

That is unusually candid for an official statistics publication, and it means the birth rates on this page are more likely to be understatements than overstatements.

The national average is not your clinic

Every licensed UK clinic publishes HFEA-validated success rates, and they vary. The HFEA's Choose a Clinic tool exists so that those figures can be compared against the national average rather than against a marketing page. Ask for the figure that matches your situation — your age band, your transfer type, your egg source — rather than the headline clinic number, which is an average across a patient mix that may look nothing like you.

Outcomes are also not evenly distributed across patients. The HFEA's own report on ethnic diversity in fertility treatment found that Black patients had a nearly 10% lower average birth rate than other patients. That is a finding about access, delays and care rather than about biology, and it is the sort of thing a single national average conceals.

Donor eggs are a different table

The figures on this page exclude treatment using donor eggs, and applying them to a donor-egg cycle would understate it, often substantially. Donor-egg outcomes track the donor's age at collection rather than the age of the person carrying the pregnancy, which is why the HFEA notes that some older patients choose donor eggs specifically to improve their chances.

This tool declines to give a number for donor-egg treatment rather than borrowing an inappropriate one. The HFEA's donation reports and your clinic's own validated figures are the right sources.

Two pieces of context that change decisions

Multiple births from IVF reached their lowest UK average yet at 4% in 2022, down from 28% in the 1990s. That fall is the direct result of single embryo transfer becoming standard practice, and it is one of the clearest public health wins in the field — twin pregnancies carry meaningfully higher risks for both mother and babies. If a clinic offers to transfer two embryos, that number is the context for the conversation.

And funding: only 27% of UK IVF cycles were NHS-funded in 2022, the lowest proportion since 2008, with sharp variation between the four nations and between English integrated care boards. Before planning a number of attempts, find out what you are entitled to where you live. The arithmetic of three transfers looks very different depending on who is paying for them.