IVF success rates: the question to ask before accepting a figure at face value

When a patient sends me three clinic leaflets, I rarely look at the percentages first. I look for the footnote. Because a success rate without its definition isn’t data – it’s a sales pitch.

Four different figures, one single word

Here’s what ‘success rate’ can mean, from the most flattering to the most honest:

• Biochemical pregnancy rate: a positive blood test. This includes pregnancies that will end a few days later. It is the highest figure and the least useful.
• Clinical pregnancy rate per transfer: a gestational sac with cardiac activity on ultrasound, relative to the number of transfers carried out. This is the figure most commonly displayed.
• Live birth rate per transfer: one child born. This is automatically lower, by ten to fifteen percentage points depending on age.
• Cumulative success rate per retrieval: the probability of having at least one child after using all the embryos from a single stimulation cycle, both fresh and frozen. This is the only figure that answers the question you are really asking.

Between the first and the last, the difference often exceeds thirty points for the same team and the same patients.

The denominators that make the figures look better

The numerator isn’t the only factor. The denominator plays a part too:

Per transfer rather than per cycle started. If a clinic cancels cycles with a poor response before egg retrieval, those patients are excluded from the calculation. The published rate rises, without any woman actually having a better chance of success.

By transfer of tested embryos. Following PGT-A, only euploid embryos are transferred: the rate per transfer naturally rises, but the rate per egg retrieval does not necessarily change. The article on PGT-A explains this point in detail.

For women under 35. An overall success rate, not broken down by age, is not relevant to you if you are 41. Always ask for the figure for your age group.

Where egg donation is combined with autologous cycles. Donation pushes the average up. The two figures must be presented separately.

The actual figures

Using your own eggs, European registers report the following live birth rates per transfer: approximately 30–35 per cent before the age of 35, 25 per cent between the ages of 35 and 37, 15 to 18 per cent between 38 and 40, 6 to 9 per cent between 41 and 42, and less than 5 per cent beyond that. With donated eggs, the rate is between 40 and 50 per cent live births per transfer, regardless of the recipient’s age, with clinical pregnancy rates of 50 to 60 per cent.

If a clinic tells you it has a 70 per cent success rate using your own eggs at the age of 42, it is not because it is better. It is because it is counting something else.

What a good clinic is willing to provide

Here are the five questions I always ask, in writing:

1. Is this rate per transfer, per egg retrieval or per cycle started?
2. Clinical pregnancy or live birth?
3. Over what period and how many cycles?
4. What is the rate for my age group, given my medical indications?
5. Does the success rate include cycles involving donor eggs?

A reputable clinic will answer without taking offence. A clinic that replies, ‘our results are excellent’, has not actually answered.

Transparency by country

Spain publishes a national register through the Spanish Fertility Society. The UK requires clinics to publish their figures via the HFEA. France publishes aggregated data via the French Biomedicine Agency. In Greece, publication by clinic is not mandatory: you have to request the figures, which is what I do for every case before recommending a clinic. This is a weakness in the Greek system, and I prefer to point it out rather than gloss over it.

And what about your own prognosis?

No average rate can describe your situation. What describes you is your age, your ovarian reserve, sperm quality, the condition of your uterus and your medical history. That’s why a comprehensive assessment always precedes a reliable estimate: the article on AMH explains the first of these factors, and a video consultation with the doctor is better than any leaflet.

Frequently asked questions

Source: https://fertilitegrece.com/en/blog/ivf-success-rates-explained/ — Triada Baloukoudis, IVF patient coordination in Greece. General information, not medical or legal advice. Printed on