Why are IVF success rates published by some fertility clinics so much higher than official statistics? Are they really so much better than other clinics?
These are questions my wife and I wrestled with. Like most people when we began the IVF process we wanted to understand our chances of having a baby. We started researching and immediately hit confusion. We had read impressive success rates on various fertility clinics’ websites but they were much higher than the official Government stats.
It took some digging but we eventually got to the bottom of things. In this post we’re going to cut through the confusion and get to the facts.
Before we start I want to make one thing clear: the aim here is not to bash (all) fertility clinics. Most clinics are run by extremely caring professionals whose primary focus is to help patients have a baby. We spoke to a number of clinics on our journey and are extremely grateful for their help.
Instead, the aim is to ensure that you have the facts. It is only by having the facts that we can make good decisions.
To help you I have developed a checklist of questions you can use when speaking to potential clinics. Simply download them below.
How some clinics massage success rates
There are many ways clinics can influence success rates. Let’s have a look at the most common.
What is success?
At first look it seems an odd question. You undergo IVF to have your own family, right? So, success is surely giving birth to a healthy baby? Not all clinics seem to think so…
Many only use “pregnancy rates” in their marketing. Why? Well, pregnancy rates are always much higher than live birth rates. This is because, unfortunately, between 17% and 22% of IVF pregnancies end in miscarriage.
Displaying higher “success rates” is, of course, better for business.
To make things more complicated, clinics can define “pregnancy” in different ways. Understanding this is important because even these give different results. Some measures show higher percentages but are much less likely to lead to a live birth.
It is no surprise, of course, that fertility clinics want to present themselves in the best possible light. There is nothing wrong with that as long as they make things clear. The problems come when the statistics they publish are misleading.
Unfortunately, this is quite common. For example, in a 2017 report the National Institute for Health heavily criticised fertility clinics for the way they used success rates.
So, the first step in getting to the real success rates is to be clear on what clinics mean when they use the terms “pregnancy rates” and “live birth rates”.
Cutting through the marketing spin, a “pregnancy” is generally defined in three ways:
This is a very early stage pregnancy, detected around 10-14 days after an embryo transfer tips. It is called “biochemical” because it is identified by looking for an increase in the level of a certain hormone (called human chorionic gonadotrophin or HCG for short). This is how home pregnancy test kits work.
If a biochemical pregnancy has been detected, about 2-6 weeks later (the timing varies depending on the clinic) an ultrasound scan will be carried out. This looks for a foetus (often called a foetal pole) and a “gestational sac” (a fluid filled structure that surrounds the foetus). If both of these are present and healthy it is called a clinical pregnancy. Depending on the timing of the scan a heartbeat may also be heard.
Assuming everything is ok with the previous scan another will be performed, usually after at least 12 weeks. The purpose of this scan is to ensure that the baby is healthy and developing well. Amongst other things the sonographer (specialist carrying the scan) will measure the foetus’s skull, check the heartbeat and examine the placenta.
Live birth rates
Fortunately, whilst there are a few definitions of pregnancy, the key thing that we are all interested in is much more straightforward. The term “live birth” simply means a baby born after at least 24 weeks of pregnancy.
Looking beyond the marketing
Getting a positive pregnancy test result – or a BFP (Big Fat Positive) – showing a biochemical pregnancy is a big step in the process. To say it is a joyous event is a massive understatement. But, it does not necessarily mean you are going to have a baby.
This is the big issue that my wife and I had with clinics that only showed pregnancy rates. Of course they are of interest but they are nothing compared to live birth rates.
No one has IVF preparation tips just to become pregnant. We put ourselves through it to become pregnant AND have a baby.
So, why do clinics use pregnancy rates to demonstrate success? The only answer we could come up with was that it gives clinics higher percentages to put in their glossy advertising.
The issue is made worse when clinics use biochemical pregnancies as the pregnancy rate measure instead of one of the others.
The first 12 weeks of pregnancy is a critical time when the chances of suffering a miscarriage are highest. As we will see later, miscarriage rates are highest (and so the chances of a live birth lowest) at the very beginning of this 12 week period. The risk reduces significantly as time passes. By the 14th week of pregnancy, studies have shown that the risk of miscarriage is less than 1%.
Of course, clinics know this and some choose to display “success rates” based on biochemical pregnancies to inflate their percentages. Studies have shown that biochemical pregnancy rates are around 20% higher than clinical pregnancy rates. In other words, 20% of biochemical pregnancies end in miscarriage even before the first ultrasound scan.
So, not only are some clinics using pregnancy rates instead of live birth rates to judge success they are also using the measure of pregnancy that has the lowest of chance of going on to produce a live birth.
This “minor detail” is sometimes lost on marketing departments who prefer to display higher figures.
Pregnancy rates based on “clinical pregnancies” more accurately reflect the chance of a live birth but they are still quite a bit higher. How much higher depends on how many weeks have passed and whether certain milestones have been reached.
Remember, overall miscarriage rates for IVF pregnancies are 17-22%. The rates drop significantly at two key milestones:
the gestational sac being visible on a scan
a heartbeat being heard
Gestational sac: at the first scan the sonographer will look for the foetus and a gestational sac. Depending on the timing, they may also look for a heartbeat. However, heartbeats are rarely detectable before week 6. Different clinics recommend having scans at different times so it may be that your first scan comes before this point.
Assuming the first scan detects a healthy foetus and gestational sac miscarriage rates drop from 17-22% to 12-15%.
Heartbeat: the second critical milestone in the first 12 weeks is the detection of a heartbeat. Once a heartbeat has been found the risk of miscarriage decreases even further. For example, one study found that once a heartbeat had been detected miscarriage rates reduced as follows:
Now we have got our heads around the terminology, to get the full picture we need to look at the “success rate” calculation.
Sounds boring? Maybe, but it is very important…
Per cycle, per after embryo transfer diet, per embryo transferred?
The number of pregnancies and live births are one part of the success rate equation. Clarity on the other part is equally important to get the true picture. Unfortunately, this is another area where “marketing” can cloud things.
I’ll use an example to explain. Let’s take a hypothetical fertility clinic that actually publishes birth rates. Let’s also say that in the latest year it helped women have 50 births. How do we calculate the success rate? We need another number to divide the 50 live births into to get a percentage.
So, let’s also imagine that the clinic had carried out 100 embryo transfers (the surgical procedures that transfer 1 or more embryos to a woman’s womb) where they transferred a total of 200 embryos.
If we calculate success rates using each of these numbers we get very different results:
Live births per embryo transfer = 50%
(50 live births / 100 embryo transfers x 100)
Live births per embryo transferred = 25%
(50 live births / 200 embryos transferred x 100)
Clearly, at first sight one is more impressive than the other.
Anything that reduces the number in the second part of the equation will increase the success rate percentage. Whilst this example uses embryo transfers to show how success rates change, the same is true if the success rates are calculated “per IVF cycle”.
On top of this, without further explanation, the use of the phrases “per embryo transfer” and “per embryo transferred” can be interpreted to mean the same thing with just a difference of present and past tense.
My wife and I already had some embryos frozen so this was a key point for us. We wanted to know clinics’ success rates for each individual embryo that they transferred. Getting the facts was not straightforward.
I contacted one very well-known clinic to clarify the stats on their website and they refused to do it. They first tried to fob me off with some vague responses so I rephrased my questions. After several emails it became clear that they did not want to give the full picture.
Needless to say, we placed our trust elsewhere.
It is not just in the definitions and calculations where success rates can be influenced. Some clinics have strict criteria before accepting patients. This can mean that couples with hard to treat issues are excluded. By excluding certain groups of patients from treatment clinics will boost their success rates.
For example, excluding patients with the following characteristics will give higher overall success rates:
above a certain age
low ovarian reserve
On the flip side, many clinics specialise in taking on “difficult” patients and this should be factored in when looking at their success rates.
During the stimulation phase you will have regular ultrasounds to monitor how your ovaries are responding. For more details have a look at our Ultimate Guide to IVF but, in essence, the doctors are looking for multiple follicles to develop on your ovaries.
If things are not going as expected the cycle may be cancelled before egg quality IVF collection. Often the reason will be to save patients money but cancelling cycles early can result in the published success rates looking better than other clinics that continue with cycles.
The key is to look at the clinic’s cancellation rates. High cancellation rates suggest that their success rates may not be accurate.
Real success rates
Let’s now cut through the marketing spin and get to the truth. By understanding the real success rates we can make better decisions about our treatment.
Fortunately, for those of us who just want the facts, independent data is available from Government authorities in certain countries.
In the UK the Human Fertilisation and Embryology Authority (HFEA) publish statistics on IVF success rates, both collectively and for individual fertility clinics. It is a great resource if you are considering any form of fertility treatment and I encourage you to visit the site.
The latest statistics are available here.
The most important stats
There are lots of numbers in the report but two of the most important are the percentage of babies born per cycle and the percentage of babies born per individual embryo transferred.
So, for women of all ages the success rates are as follows:
The reason for the difference between the two measures is that in certain circumstances multiple embryos are transferred rather than 1 and this increases the chances. We covered this subject in detail in our Ultimate Guide to IVF.
The age factor
One thing that jumps out from all the statistics is the impact that a woman’s age has on success rates. This is best shown by looking at the live birth rates per what to eat after embryo transfer. Using the HFEA data and breaking things down into different age groups we can see that the younger you are the better the chances of success:
HFEA Live Birth Success Rates By Age
There are two things to note about this table:
age is taken at the time embryos are created, not at the time when they are transferred
the percentage for over 44s is skewed because many patients of this age decide to use embryos donated by younger women rather than their own
It is worth mentioning here that it is not just a woman’s age that can affect IVF success rates. A man’s age is also important. This area is not as well studied but it is known that men’s age reduces the chances of becoming pregnant naturally.
A recent study has shown that it also impacts IVF success. Researchers at Harvard University examined nearly 19,000 IVF cycles and found that men aged between 40 and 42 had a 46% lower chance of having a baby than men aged between 30 and 35 where the female partner was under 30.
Frozen embryos & thawing
For anyone undergoing a frozen embryo cycle there is an additional factor to consider: will the embryos survive the free-thaw process?
Looking at the stats above it may appear that frozen embryos are more effective than fresh in IVF. The reason for this is partly because frozen preparing for embryo transfer usually take place sometime after the stimulation phase (see our Ultimate Guide to IVF for more on the IVF process). The stimulation phase involves taking drugs to encourage your body to produce more eggs than it would do naturally. The problem is, these drugs are not always great for your womb.
In a fresh cycle the transfer would happen a few days after stimulation finishes. In frozen cycles it is usually several weeks, months or years before transfer and during this time your body has the chance to recover from stimulation. This often leads to better conditions in your womb for the embryos which means that they are more likely to implant and develop into a pregnancy.
However, the figures in the above table do not take into account embryos that are damaged during the freeze-thaw process (cryopreservation to give it the fancy name).
With improvements in technology over the last decade the freeze-thaw process is less likely to harm embryos that are stored for later use. There is, however, still a risk, particularly if the clinic is using out-dated technology.
My wife and I stored our embryos back in 2008. With the technology used at the time around 80% of embryos survived the freeze-thaw process. With modern quick free-thaw technology between 84% and 95% of embryos survive.
If you are considering a frozen embryo cycle first factor in the risk of embryos not surviving the process and, second, check that your clinic uses the latest freeze-thaw technology.
Do your research
I hope that this post has shed some light on what can be a confusing area. There are so many ways that clinics present results in their marketing that it can often be difficult to get to the truth.
Don’t allow IVF clinics to dazzle you with glossy brochures and fancy waiting rooms. Look beyond the veneer to get the truth.
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In some countries clinics are required to report success rates to Government authorities. If this is the case in your country I encourage you to visit their websites to verify the stats. For example, in the UK data is available on the HFEA website by searching for the clinic.
In the US it is available on the Center for Disease Control and Prevention (CDC) website:
and the Society for Assisted Reproductive Techniques (if the clinic is a member – 80% are).
The one downside of these sites is that they only show basic data. To overcome this, I have compiled a list of questions that you can ask fertility clinics to help you get to the facts. This will enable you to decide if the clinic is right for you.