IVF clinics are legally required to report their outcomes to the HFEA, which publishes this data annually on its website. In theory, this gives patients a standardised basis for comparison. In practice, the data is easy to misread — and clinic marketing materials often present it in ways that make outcomes look better than they are.

This guide explains exactly what the HFEA measures, what each figure means, and how to use the data to make an honest comparison.

What the HFEA Measures

The HFEA collects data on every IVF and ICSI cycle carried out in licensed UK clinics. The key metrics it publishes are:

Live birth rate per embryo transfer. The percentage of embryo transfers that result in a baby being born. This is the most clinically meaningful figure for a patient because it counts actual babies, not positive pregnancy tests.

Live birth rate per cycle started. The percentage of cycles (from the beginning of stimulation) that result in a live birth. This is a lower figure than per-transfer rate because some cycles are cancelled before transfer — either because stimulation produces no eggs, no embryos develop to the transfer stage, or the embryos are frozen for later transfer.

Positive pregnancy rate. The percentage of transfers resulting in a positive beta-hCG blood test. This is higher than the live birth rate because not all clinical pregnancies result in a live birth.

The HFEA publishes these figures broken down by age group, clinic, and treatment type (own eggs vs donor eggs, fresh vs frozen transfer). The age group breakdown is the most important variable for interpreting results.

The Metrics Clinics Use — and Why They Differ

Clinics often present their success rates differently from the HFEA's published figures. Common variations:

Cumulative success rate per patient. Some clinics report the probability of a patient achieving a live birth over multiple cycles — for example, "64% of our patients achieve a live birth within three cycles." This figure is meaningfully higher than the per-transfer rate and is not directly comparable between clinics because it depends on how many cycles are included.

"Clinical pregnancy rate." A clinical pregnancy is one confirmed by ultrasound (heartbeat visible). This is higher than the live birth rate because some pregnancies are lost after the ultrasound stage. When a clinic reports its "pregnancy rate," ask whether this means live births or clinical pregnancies.

Selected age groups. A clinic may report success rates for "all patients" when its casemix is skewed toward younger patients. Alternatively, it may cherry-pick its best-performing age group. The only meaningful comparison is the live birth rate per transfer for your specific age group.

Fresh vs frozen transfers combined. Frozen embryo transfers (FETs) generally have comparable or slightly higher success rates than fresh transfers in recent HFEA data, because they allow the uterine lining to recover from stimulation before transfer. Combining fresh and frozen results can obscure how each performs individually.

What "Per Transfer" vs "Per Cycle Started" Actually Means

Consider two patients, both aged 35:

Patient A starts a stimulated IVF cycle, produces three eggs, fertilises two, transfers one fresh embryo and has one frozen. Her fresh transfer fails, but her frozen embryo transfer (FET) succeeds and results in a live birth.

In HFEA terms:

  • One cycle started
  • Two embryo transfers (one fresh, one FET)
  • One live birth
  • Per cycle started: 100% success (one live birth from one cycle)
  • Per transfer: 50% success (one live birth from two transfers)

Patient B starts a cycle, produces no eggs, and the cycle is cancelled. No transfer occurs.

In HFEA terms:

  • One cycle started
  • Zero transfers
  • Zero live births
  • Per cycle started: 0%
  • Per transfer: undefined (cannot divide by zero)

Per-transfer rates exclude patients like Patient B, whose cycles were cancelled before transfer. Per-cycle-started rates include them. This is why per-cycle-started rates are generally lower than per-transfer rates — they capture the patients for whom treatment failed even before a transfer was possible.

For most patients, per-transfer rate is the more useful planning figure. It tells you what your chances are if you get to the point of having an embryo to transfer.

HFEA Success Rates by Age: What the 2024 Data Shows

The following live birth rates per fresh embryo transfer are approximate figures from HFEA 2024 data for IVF using the patient's own eggs:

| Age group | Live birth rate per transfer | |---|---| | Under 35 | ~32% | | 35–37 | ~25% | | 38–39 | ~18% | | 40–42 | ~10–12% | | 43–44 | ~5% | | 45+ | <3% |

For donor egg IVF (using a donor under 35), rates are broadly similar across recipient age groups — approximately 28–32% per transfer — because the key variable is the donor's egg quality, not the recipient's.

These figures are national averages. Individual clinic rates vary around these averages. A clinic with a significantly higher rate than the national average for your age group may genuinely achieve better results — or may treat a younger, lower-risk casemix. A clinic with a significantly lower rate warrants scrutiny.

For a discussion of how these rates affect financial planning for older patients, see IVF after 40 in the UK.

How to Use the HFEA Website to Compare Clinics

The HFEA's Choose a Fertility Clinic tool (available at hfea.gov.uk) allows you to compare clinics by:

  • Live birth rate per embryo transfer (fresh and frozen separately)
  • Number of cycles performed (a larger volume generally indicates more experience)
  • Overall inspection rating

When comparing:

  • Always compare the same metric (live birth rate, not pregnancy rate)
  • Always compare the same age group
  • Always compare the same treatment type (own eggs vs donor eggs)
  • Look at both the rate and the number of cycles on which it is based — a very high rate from a small number of cycles is statistically less reliable

Also check when the data was collected. Clinic staffing, protocols, and equipment change, and data that is two or three years old may not reflect the clinic's current performance.

Success Rates and Add-On Treatments

Some clinics present their overall success rate as evidence that add-on treatments work — "our rate is above the national average, and we offer X add-on." This is correlation, not causation. The clinic's casemix, patient selection, and main treatment protocols are far more likely to drive outcome differences than any specific add-on.

For a detailed assessment of which add-ons have genuine evidence of benefit, see IVF add-on treatments and the evidence.

Frequently Asked Questions

Q: A clinic told me their success rate is 60%. How is that possible when the national average is much lower?

A: The figure is almost certainly not a live birth rate per transfer for an age-representative population. It may be a cumulative rate over multiple cycles, a positive pregnancy rate rather than a live birth rate, or based on a selected age group. Ask specifically: live birth rate, per transfer, for patients in your age group, in the most recent full year of HFEA data.

Q: Can I trust the HFEA data?

A: The HFEA requires clinics to submit data and audits reporting accuracy. The data is the most reliable publicly available outcome information for UK fertility treatment. It is not perfect — some clinics have been found to have reporting issues — but it is the best standardised source available.

Q: Should I choose the clinic with the highest success rate?

A: Not necessarily. A high success rate may reflect a younger casemix or more selective patient acceptance rather than better treatment. Also consider proximity (particularly relevant if you will be attending for monitoring scans frequently), waiting times, patient experience, and whether the specific treatments you need are offered.

Q: What does "multiple birth rate" mean and why does it matter?

A: IVF with multiple embryo transfers increases the risk of twins or triplets, which carry significant health risks for mother and babies. The HFEA reports clinics' multiple birth rates alongside success rates. A lower multiple birth rate — ideally close to the national single embryo transfer target — indicates a clinic follows safer transfer practices.

Q: If my clinic's success rate is below average, should I switch?

A: Not necessarily on the basis of one metric alone. Discuss the data with your consultant, understand the clinic's case mix, and consider whether you are in a higher-risk group that would naturally have lower rates. That said, if a clinic's rate is persistently and materially below the national average with no clear explanation, it is a legitimate factor in your decision.

This article is for information only and does not constitute medical or legal advice. HFEA data is updated annually; always check hfea.gov.uk for the most current figures.