IVF Success Rates: What the Numbers Actually Mean

Birth rate vs pregnancy rate — and why it matters

A positive pregnancy test after embryo transfer is not the same as taking a baby home. Biochemical pregnancies, miscarriages and ectopic pregnancies all sit between those two outcomes. When the HFEA reports success rates, they report birth rates — live births per embryo transferred or per egg collection. That's the number that actually matters. If a clinic's marketing materials talk about 'pregnancy rates' without specifying live births, that's worth questioning.

Age is the single biggest variable

The HFEA breaks success rates into age bands for good reason. A clinic's birth rate for patients under 35 will typically be 30–45%. For patients aged 38–39, it drops to 20–30%. Over 42, it falls below 10% at most clinics. This isn't the clinic's fault — it's biology. Egg quality declines with age, and no amount of clinical expertise can fully compensate for that.

This is why comparing a clinic's headline rate without knowing the age breakdown is misleading. A clinic that treats a younger patient population will naturally report higher overall rates. It doesn't mean they're better — it means their patients were younger.

Per egg collection vs per embryo transfer

This distinction trips people up. Birth rate per egg collection includes every cycle that started — even those where no embryos were suitable for transfer. Birth rate per embryo transfer only counts cycles where an embryo was actually put back. The second number will always be higher, because it excludes failed cycles.

Per egg collection is the more honest measure. It tells you: if I start a cycle at this clinic, what's my chance of ending up with a baby? That's the question most patients are actually asking.

Small sample sizes distort everything

A clinic that performed 20 cycles last year and had 12 births can report a 60% success rate. A clinic that performed 800 cycles with 280 births reports 35%. Which clinic is actually better? Impossible to say from one year's data. Small clinics have wildly volatile statistics — one or two lucky outcomes can swing the rate by 20 percentage points. The HFEA now requires a minimum cycle count before publishing rates, but it's still worth checking volume alongside percentages.

Frozen vs fresh — the landscape has changed

Ten years ago, fresh embryo transfers had significantly higher success rates than frozen. That gap has almost closed. Modern vitrification techniques mean frozen embryo transfers now achieve comparable birth rates at many clinics, and some argue they're better because the uterine lining has time to recover from stimulation. When comparing clinics, look at both frozen and fresh rates — a clinic that does mostly freeze-all cycles might look worse on fresh transfer stats but have excellent outcomes overall.

What the HFEA doesn't capture

The HFEA data has a significant time lag — typically two to three years. A clinic that hired a new embryology team or upgraded its lab equipment last year won't see that reflected in published rates yet. Conversely, a clinic that lost key staff could still be trading on outdated numbers. The data is the best starting point we have, but it's a historical snapshot, not a live feed.

How to use success rates when choosing a clinic

Compare birth rates per egg collection for your age group. Check the clinic's cycle volume — higher volume generally means more reliable statistics. Look at the trend over multiple years if available. And remember that success rates are one factor among several: location, cost, waiting times, communication quality and the specific treatment protocols offered all matter too.

On Vero Fertility, we show birth rate per egg collection broken down by age band for every UK clinic, alongside verified pricing. That combination — outcomes and cost together — lets you calculate cost per live birth, which is the single most useful metric for comparing clinics on value.