A friend recently told me that I should feel more optimistic about my chances of success with IVF. After all, she said, I was still young, and age is one of the most important predictors of success. While certainly true, the chance of having an actual baby to take home after a round of IVF is still far less than 50%.
I used to think that needing IVF to get pregnant was a worst-case scenario, “well if I can’t get pregnant naturally, I’ll still be able to get pregnant using IVF”.
Poor naive me!
The Definition of Success
To start off, we need to define success. We, the patient, would define a healthy baby as the true measure of success. Getting pregnant is obviously the first step, but unfortunately, about 10-25% of pregnancies end in a miscarriage. Depending on the clinic, IVF success rates are defined as either:
- A positive pregnancy test
- Clinical pregnancy (defined by fetal heartbeat)
- Live birth
Say Clinic A boasts about their 50% success rate and Clinic B reports a 40% rate, we can only compare them if they defined success the same way. So get comfortable reading the fine print (great job, you’re doing it already!). And if they aren’t being upfront? Just ask them straight up for specifics.
What influences IVF success rates?
There are so many other factors that can influence IVF success rates. Let’s focus on the most important ones. Age plays a very important factor. If you’re a 40-year-old, a success rate that’s based on women aged 34 and under is just not useful.
Just like your best friends’ Tinder profile pics, infertility clinics will try to impress you by showing only the prettiest of stats, omitting all the ugly ones.
Let’s take a look at the most important players:
- Age (yup, that’s a biggie!)
- Number of embryos transferred
- Type of infertility diagnosis
- Genetic factors
- Use of your own eggs/sperm vs use of a donors eggs/sperm
- Fresh or frozen cycles
- Transfer of a 3-day or 5-day embryo
IVF Success rates per cycle or per transfer
All 464 (as of 2017) fertility clinics in the US have to report their data to the CDC every year. The latest results are actually from 2 years ago (both due to the clinic having to wait to find out the final outcome of a cycle as well as the time it takes to collect and analyze the data). The 2015 data can be found on the CDC website.
Let’s take a closer look at the top part of the 2015 national summary, the success rates of a fresh embryo cycle. The bottom part [not shown here] lists the frozen embryo rates, banking cycles, and the donor egg success rates, which all deserve a post of their own.
Source: CDC’s ART 2015 National Summary Report.
How many cycles are canceled?
The CDC data shows that between 6.5% and 23.8% of cycles are canceled before egg retrieval even takes place. While that is interesting, most of us know that we should be far more worried about the cycle being canceled before transfer.
Some of the reasons a cycle may be canceled before embryo transfer:
- Not enough eggs retrieved
- Low fertilization rates after retrieval
- No embryos left that made it to day 3 or day 5
Unfortunately, the CDC does not give us those percentages. But we do know the number of cycles that did, in fact, make it to transfer day. With a few quick calculations, we can figure out the percentages we’re looking for (the total number of canceled cycles!). Take a look:
On average, 34.9% of all initiated cycles don’t make it to transfer. That’s way worse than the cancellation rates the CDC reports, simply because they only look at cancellations before egg retrieval.
Fertility clinics love to tout their amazing success rates in marketing material and on their websites. Most of ’em show actual statistics of over 50% success! The unsuspecting potential patient will gobble it all up and sign on the dotted line right then and there. But, as you can imagine, if you start tracking whether a cycle was a “success” or not after transfer has already occurred, you can see how success rates can look a bit rosy (to put it mildly).
I can’t stress enough how important it is to take into account that quite a few cycles don’t even make it to transfer. I’ve read many stories of heartbroken couples who didn’t have a single embryo left to transfer.
Clinics’ IVF success rates are often artificially boosted by being derived from the number pregnancies following a successful transfer. Don’t forget that a third of IVF cycles don’t lead to transfer. So be aware and do your research before you decide which clinic to sign up with. When in doubt, look ’em up on the CDC website, almost all data is there.
Chance of becoming pregnant per IVF cycle
As we now know, it’s important to take into account that cycles may not make it to transfer day. All that matters is what the odds are on day 1 of the IVF cycle that you end up getting pregnant.
Depending on the age group you belong to, you have a 29.3% chance of getting pregnant (between 2.7% and 38.3%). Age is clearly one of the best predictors of success.
The CDC sums it up nicely by showing that of all 91,090 cycles started in 2015, 70.2% did not result in pregnancy.
Source: CDC’s ART 2015 National Summary Report.
Chance of miscarriage, stillbirth, induced abortion and other bad stuff
Unfortunately, just like with a spontaneous pregnancy, there’s a chance you will have a miscarriage. Of all the reasons why a pregnancy does not lead to a live birth, miscarriages make up the largest proportion. The numbers below also include stillbirths and induced abortions.
Let’s take a look at the difference between the number of pregnancies and the total number of live births.
Even after overcoming the hurdles of:
- not having your cycle canceled before retrieval
- having enough embryos survive to transfer day
- getting that long-awaited positive pregnancy test
… there’s still an 18.5% chance (between 13.6% and 71.2%) that the pregnancy never makes it to a live birth.
Chance of live birth per IVF cycle
I think we can all agree that the only success rate we really care about is the chance of a live birth. So let’s take a closer look and see what your chances at the start of your IVF cycle are of delivering a baby 9 months later:
As you can see, on average, there’s about a 23.9% chance that your IVF cycle results in a live birth, but the numbers range from 33.1% for those <35 years old, to 0.8% for those over the age of 44. That’s a pretty significant difference.
Furthermore, you’ll notice that there are still a lot of twin births, something that, with all the risks involved, isn’t something you should hope for. The chance of a normal weight singleton that isn’t born prematurely is only 15.5% (ranging from 0.6% to 21.3%).
After attempting to bore you to death with these long tables, let me try to summarize all findings with a couple of graphs instead.
The following figure shows us just how important age is when considering IVF outcomes using your own eggs. The negative effect of age is reversed when using (young) donor eggs, something we’ll discuss in another post.
The next graph shows us some of the things that we don’t want to see happening when starting IVF: cycle cancellations and the percentage of pregnancies that don’t make it to a live birth (mostly due to miscarriages).
Here, we see the opposite of what we saw in the graph above, with increased chances as you move up in age brackets.
Finally, and perhaps most importantly, this chart depicts the stark difference in live birth rates when you start counting at either the start of the IVF cycle or at the transfer stage. As you can see, things start to look a lot better once you and your embryos make it to the transfer stage of the IVF cycle (ie. your cycle wasn’t canceled beforehand). The chances of a live birth reach almost 50% in women below the age of 35.
That being said, none of these statistics really matter that much when it comes down to it. On a personal level, it’ll either work, or it won’t.
CDC vs SART and cumulative live birth rates
Before we conclude this post, I quickly want to mention the other organization that publishes yearly IVF success rates; the Society for Assisted Reproductive Technology (SART). As of November 2017, their preliminary national summary report of 2015 can be found here.
Not all fertility clinics report to SART, so the data is somewhat less complete than the CDC data. The SART data can’t easily be compared to that of the CDC because they’re using different outcomes.
The CDC looks at the success rate of each started IVF cycle, while SART looks at the cumulative success rates of each IVF cycle. So if your egg retrieval session leads to 4 embryos that looked good enough to freeze, you essentially have 4 tries to get pregnant, all counting towards the success rate of that single egg retrieval session.
Lots of clinics leave out the fact that the IVF success rates they report are based on cumulative success rates, which patients often don’t realize. While some might argue that it doesn’t really matter, it does matter when you take into account the cost (you’re not just paying for an IVF cycle, but also a couple of thousands each time you attempt another embryo transfers) and the time it takes to get pregnant/have a baby. And most importantly, let’s not forget about the heartache that accompanies every failed try!
So now that you know the real numbers, do you feel better or worse?
Me personally, I’m glad I know. I can only imagine the sadness that must follow a failed cycle after having very high expectations. Now that I know that there’s a pretty big chance of any particular cycle not working out, I feel a lot more relaxed. There’s less pressure, less anxiety and overall, I just feel that I’m in a better position to handle whatever comes next.
I’m fully aware it might take multiple tries to become pregnant, and I’m also aware that it may not even happen at all. I’ve come to accept all of that (well… as much as possible) and I’m am still excited to see what happens with my very first IVF experience.