I’m about to break the “website rules” in a big way: I’m going to give you the nutshellised version of this entire article right at the start, so if you don’t have time or you’re panicking like mad or you can’t be bothered to wade through a 3,500-word diatribe against certain private clinics, you don’t have to.

Here’s the nutshellised version:

  • If you want to look at the success rates of individual clinics, please please please use the HFEA website – which has an info page on every clinic in the country – to do so. Some clinics are incredibly cheeky with how they select and present their data, but the HFEA standardises everything and allows you to accurately compare them all.

    (The HFEA certainly isn’t controversy-free – and I have my issues with how it operates – but it’s useful for comparing like-for-like data across fertility clinics.)

  • Most importantly, try not to obsess over success rates when choosing a clinic. There are far more important factors to consider.

Want more detail? Here you go:

First up: what does “success rate” actually mean?

In this article, “success rate” means “live births per embryo transferred”. It’s the preferred method of the Human Fertilisation and Embryology Authority (HFEA) for assessing IVF success, and I agree that it’s the most useful measure in most instances. I’ll get into this in more detail soon.

The HFEA also publishes stats on “live births per egg collection” for each clinic, which “… shows the chance of success from all the fresh and frozen embryo transfers within two years of one egg collection. Whilst births per embryo gives you an indication of success rates for just one embryo transfer, births per egg collection gives an overall picture of success rates for a full course of treatment (which can include one fresh and a number of frozen transfers).”

There are two reasons I’m not focusing on “births per egg collection” today:

  1. There are enough numbers flying around this article already! I don’t want to make things even harder to follow.

  2. The “per egg collection” stat is more useful for women who are able to produce tons of eggs and have the funds to pay for many embryo transfers, if necessary. (Each separate transfer at a private clinic costs extra.) If you don’t produce many eggs, or can’t afford too many transfers, or you simply want to get pregnant ASAP, the “per egg collection” stat feels more like a kick in the teeth than anything else.

What’s the national average success rate for IVF?

The below percentages are from the HFEA (2016 data). They show the average chance of a live birth after IVF treatment per fresh embryo transferred, using a woman’s own eggs and partner’s own sperm:

  • Aged under 35: 29%
  • 35-37: 23%
  • 38-39: 15%
  • 40-42: 9%
  • 43-44: 3%
  • Aged over 44: 2%

If you’d like average (across all clinics) data on frozen transfers, donor eggs, donor sperm, and other variables, you can check the HFEA’s Fertility Trends report. I’ll be using the above data as my benchmark throughout this article, purely for consistency and so I can show what private IVF clinics do to make their own success rate numbers look better than they really are.

Most UK IVF clinics do a good job 

Of the 74 clinics in the UK that provide private fertility treatment…

  • 2 clinics have success rates that are above the national average (NURTURE Fertility, Nottingham; CARE Northampton).
  • 2 clinics have success rates that are below the national average (Wales Fertility Institute, Cardiff; Salisbury Fertility Centre).
  • 6 clinics are too new to have success rates yet (Thames Valley Fertility; IVF London; CREATE Fertility, Manchester; CREATE Fertility, Bristol; CARE Fertility, Birmingham; Bourn Hall Clinic, Wickford).
  • 1 clinic doesn’t have any success rates and I’m not sure why (Hewitt Fertility Centre, Knutsford).
  • All remaining clinics have success rates that are consistent with the national averages mentioned above (meaning they’re just a few percentage points in either direction from the average).

(“Above”, “below” and “consistent with” are calculated by averaging out the success rates for each age group within a clinic.)

Now… you should know that the HFEA considers a success rate to be “consistent with the national average” as long as it's 10% in either direction of the average. That means one clinic could have a success rate of 20% for under 35s and another could have a success rate of 38% (for the same age group), and they'd both be considered “consistent with the national average”. BUT, as the HFEA says, “… most clinics are broadly all as good as each other – small differences in rates are usually down to the different types of patients treated.”

This is an important point. 

About those “small differences”…

Some clinics, for example, won’t treat anyone with a BMI over 30: a high BMI negatively affects IVF success, no matter how good the clinic is. Clinics that treat women with a high BMI are more likely to have lower success rates than pickier clinics.

Statistics are further skewed (albeit slightly) when clinics treat both private and NHS patients. The NHS has much stricter selection criteria, favouring women who have a higher chance of success. The clinics that accept NHS patients are therefore likely to have slightly higher success rates compared to private-only clinics.

(You might also wonder about age: it’s the most important factor in determining IVF success, so a clinic that treats all age groups is likely to have lower success rates than a clinic that only treats women under the age of 37. That’s true, but the HFEA addresses this already by separating out clinic data into age ranges – so you can see success rates per age group and don’t need to worry about skewed stats.)

Many private IVF clinic websites have misleading information about their “success rates”

So… clinics aren't drasticallky dissimilar from each other when it comes to success rates. Annoyingly (but understandably) that doesn’t stop them from trying to pretend they’re better. Take Herts & Essex Fertility Centre. If we compare the HFEA data with the data on the clinic’s website, things look… weird. Here’s one example:

HFEA data:

  • Live births per embryo transferred (age <38): 27%, which is consistent with the national average

Herts & Essex Fertility Centre data:

  • Live births per embryo transfer (age 20–34): 44.7%
  • Live births per embryo transfer (age 35–37): 42.9%

(Combined, these represent the age groups covered by the HFEA data.)

44.7% and 42.9% are nowhere near the 27% stated by the HFEA. So what’s going on?

Three letters is what’s going on. The clinic uses the word “transfer”, whereas the HFEA uses “transferred”. Those three letters make a huge difference.

Here’s how Herts & Essex explained it in an email they sent me:

“The reason for the difference in success rates is because the HFEA data is showing live birth per embryo transferred, whereas the data on our website is showing rates per embryo transfer event, so in actuality are not showing the same thing. [Note that their website doesn’t say “embryo transfer event”; it just says “embryo transfer”.]

Essentially, the differences come from what a measurement of ‘success' is. For example, if a patient were to have a single live birth following the transfer of two embryos, this would be a 50% success rate per embryo transferred because only one of the two embryos implanted. However, according to success rate per embryo transfer event, this would be 100% successful. Similarly, if a patient were to have a singleton live birth following the transfer of three embryos, according to success rate per embryo transferred, this would be a 33% success rate but a 100% success rate according to success per embryo transfer event.”

While this explanation makes sense, there’s a good chance many potential patients will be misled by the Herts & Essex Fertility data. As I said in my reply:

“Don't you think it's misleading to publish ‘per embryo transfer' rather than ‘per embryo transferred'? Surely lots of people are going to compare your stats to other clinics that cite ‘per embryo transferred' and think your clinic has much higher success rates – when actually they're comparing two very different measures?

If nothing else, shouldn't there be an explanation of this difference on your ‘success rates' page?

From what I understand, the HFEA encourages clinics to publish ‘per embryo transferred' data because it wants to deter you from transferring multiple embryos.” [More on this final point shortly.]

I’ve picked on Herts & Essex Fertility because it was one of the first I came across, but believe me: many other clinics are just as sneaky.

Keep reading… there's more below.

Misleading success rates are problematic for another reason

The HFEA has a good reason for preferring the “live births per embryo transferred” statistic:

“Birth rates per embryo transferred (PET)… helps patients and clinics to recognise that whilst transferring more than one embryo at a time is thought to raise success rates, it also raises the chance of twins, which can carry health risks for the babies and mother.”

I won’t go off on a tangent about the health risks associated with multiple pregnancies in this particular article, but you can read more here.

In 2016, the HFEA reported that its efforts to encourage clinics to reduce multiple birth rates has been successful: “In 2008, one in four pregnancies from IVF resulted in a multiple birth, leading us to set a target that no more than 10% of IVF births should be multiples. Working together with patient groups, clinics and professional bodies, the national multiple birth rate has decreased from 24% in 2008 to 11% today, without reducing birth rates [my emphasis].”

Indeed, it seems single embryo transfers aren’t necessarily less successful. In a 2010 meta-analysis, the BMJ discovered that “An additional frozen single embryo transfer [after a failed fresh transfer] resulted in a cumulative live birth rate not significantly lower than the rate after one fresh double embryo transfer”.

That is: “1 embryo fresh transfer” + “1 embryo frozen transfer” = very similar live birth rates to “2 embryos fresh transfer”

Yes, it takes longer to do things this way – but it’s safer. Nevertheless, many clinics continue to refer to success rates that are based on “per embryo transfer event” rather than “per embryo transferred”. As explained earlier, that incentivises them to transfer multiple embryos rather than just one – which is generally NOT in the interests of patients.

It’s possible this is just a theory: clinics that report “per embryo transfer event” might not, in fact, perform more multiple embryo transfers than the national average.

But… well… they do.

I’ve checked the data of many private clinics in the UK, and the ones that report “per embryo transfer event” (which is the same as “per embryo transfer”) on their website tend to have higher multiple birth rates.

While it sometimes makes sense for older women (and a small minority of younger women) to have a multiple embryo transfer, the clinics I looked at have a high multiple birth rate across all age groups – not just older women. Not only that, but many of them (including Fertility Plus, CRGW, City Fertility and many more) also have slightly lower birth rates per embryo transferred than the national average. (Not significantly lower, I must add: they’re still considered “consistent” with the national average.)

I came across one clinic that has INSANE results on the HFEA website (turns out there’s been quite a lot of press coverage about it). The Assisted Reproduction and Gynaecology Centre in London has fairly standard results for “live births per embryo transferred”, yet its multiple birth rate is higher than anything I’ve ever seen for patients under the age of 38:

(The national average is now 11% rather than 14%. I’m assuming the HFEA hasn’t updated its charts yet.)

This implies the doctors at the clinic are shoving a buttload of embryos up almost all patients – both young and older. Interestingly, this clinic’s website provides success rates on “clinical pregnancy per cycle started”, which is a confusing measure that most clinics don’t bother publishing (or at least will publish alongside other types of data – like “per embyo transferred”). There’s more about measuring “per cycle started” below.

There are plenty of other ways in which clinics get cheeky with their success rates

Clinics know you’ll look at their “success rates” page – and they want you to think they’re superior to their local competitors. So they’ll often do whatever it takes to present their data in the best possible light.

Here are some other tactics to watch out for:

  • They’ll combine patient age groups in any way that will help bump up the numbers.

  • Instead of publishing birth rates, they’ll publish pregnancy rates if it makes them look better. While this is a totally legitimate way to measure things, you just need to make sure you don’t compare it to birth rates on another clinic’s site.

    CARE London, for example, makes a huge deal of its “High IVF Results in London!” and shows off an impressive-looking chart displaying “clinical pregnancies per embryo transferred”. But click on “More results” (and kudos to them for including extra stats at all on their website) and you’re faced with the reality that “Live birth rates per embryo transferred” are less impressive. In fact, they’re slightly lower than the national average, for every age group.

    Fertility Plus in London does the same thing. It mentions a 42% clinical pregnancy rate on its website, but its “live birth rate per embryo transferred” (published on the HFEA website) is slightly lower than the national average.

  • They’ll publish stats for “embryo transfer” (or “embryo transfer event”), not “embryo transferred”. See above for more on this.

  • They’ll compare their own success rates to the national average – but only when theirs looks better. Otherwise, they won’t mention the national average.

    City Fertility (also in London) cleverly compares itself to other clinics for donated egg cycles only – where the clinic seems to excel. For IVF cycles using women’s own eggs, the clinic a) only provides clinical pregnancy rates, not birth rates, and b) decided not to compare itself with other clinics. The clinic’s live birth rates are slightly lower than the national average, according to the HFEA, so that might be why.

    Salisbury Fertility Centre (one of the only two clinics that has success rates officially deemed “below the national average”) does something similar. Once your eyes adjust to the chaos of its “success” page, you’ll see that it compares just one of its data points to the national average (where it can make itself look superior). None of the other numbers on the page are compared to the national average – and they all use completely different measurement techniques (some are “per embryo transferred”, some are “per transfer procedure”, some are “clinical pregnancy” rates, some are “live birth” rates, etc.).

  • Their stats will be “per treatment cycle”, which is bloomin’ confusing because it means different things to different people. For most private clinics, it’s the same as an “embryo transfer event”, but for the HFEA, it refers to any IVF treatment that has begun – even if an embryo transfer doesn’t end up happening (e.g. because the patient didn’t react to the stimulation drugs).

  • They’ll be extraordinarily vague – to an infuriating degree. I feel the need to include a few screenshots so you can be just as furious as I am:

    Gennet (which has a clinic in London):

WHAT DOES THIS MEAN????!!!! ARGGGHHH!

Harley Street Fertility Clinic:


52% per embryo transferred? Per embryo transfer cycle? Per treatment cycle? Per eggs collected? Fresh? Frozen? Donor eggs? Donor sperm? Live births? Clinical pregnancies? Who flipping knows.

The Fertility & Gynaecology Academy

Are we talking clinical pregnancy rates per embryo transferred or per embryo transfer treatment?

Keep reading… there's more below.

There are more important factors than success rates

At the beginning of this article, I said that almost all clinics have similarish success rates: trying to pick a private IVF clinic by success rate alone is like trying to bet on a horse based on the number of legs it has. The intervening 1,500 words were to show how clinics attempt to give the impression that they have far superior rates compared to the national average.

So now you know all that, how do you choose a private IVF fertility clinic if you can’t base your decision on success rates?

The following list is a good place to start. Figure out which of these factors are important to you when choosing your ideal private fertility clinic:

  • Positive reviews and ratings from former patients are always a good sign. Look at the patient ratings on the HFEA site, but also on Google and the clinic’s Facebook page. (But bear in mind that the most and least satisfied patients are more inclined to leave a review than those who thought the service was “fine” – so take all ratings and reviews with a pinch of salt.)

    Three other places to look are the message boards on Mumsnet, BabyCentre and HealthUnlocked: search for the name of your clinic and you’re sure to find thoughts, reviews and anecdotes from former and current patients.

  • How much does treatment cost? Fertility clinics are free to set their own costs, which means the same treatment could be markedly more expensive in one place compared to another down the street. (Competition should put the kibosh on that sort of thing, but it doesn’t always.)

    Beware, though: different clinics have different ways of presenting the cost of treatment to you, and you need to make sure you’re doing an accurate comparison. My article on private IVF costs explains everything and shows how to compare costs across clinics.

  • Figure out whether you’re eligible for treatment there: some clinics have stricter criteria than others. E.g. at ABC IVF in London, you need to be aged 37 or under, have a BMI that’s under 30, and have a normal/good ovarian reserve.

  • Is it important to you that they offer a comprehensive counselling service – either free or for a fee – as part of your treatment? Many clinics offer this, but not all. The HFEA page for each clinic tells you what kinds of counselling (if any) are available.

  • Do you need a clinic that’s open late/early/at the weekend, to accommodate your job/ other responsibilities? Some clinics have broader opening hours than others, but you’ll need to ask rather than rely on the information on their website: those morning/evening/weekend hours could be reserved for procedures like egg retrieval rather than general scan or blood test appointments.

  • Is it important that you only see female doctors? The HFEA page for each clinic tells you whether a female doctor is available.

  • Is parking essential? The HFEA page for each clinic will show if parking is available.

  • Do you need help with funding? Many clinics offer “baby or your money back” schemes – which have been getting more and more generous over the years. (Be sure to read the fine print, though!) This article contains more information about funding options for IVF.

  • Another funding option: many clinics now partner up with loan companies to offer specialist IVF loans. Not all clinics offer it, though, so you need to check with all the places on your shortlist.

  • Be wary of any clinics that push you to bump up the cost of your treatment with various add-ons like embryo glue and assisted hatching. While there’s some evidence that these add-ons work for some people, they’re certainly not the miracle cures that some people make them out to be. (Read my article about IVF add-ons and various fertility supplements here.)

Have any questions? Tell me!

Lots of readers asked me about success rates, and I figured it would be pretty easy to do the research and write up my findings. I was wrong: this subject is a minefield.

If you don’t understand anything I’ve written or need more information on something, there’s a good chance you’re not alone – so please tell me and I’ll do my best to re-explain or do some more research: mish@theduff.co.uk. I want to make sure this article answers all your questions and gives you the confidence you need to pick a private IVF clinic that suits your needs.

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