Written by Jenny Wordsworth, LLB (Hons), Reviewed by Dr Phoebe Howells. 

 

Setting realistic expectations matters when you start IVF. Here, I walk through what I wish I had known before my own IVF. This includes the "IVF funnel": what happens at each stage, from egg collection to bringing a baby home, and what the UK data actually says about your chances.

Why Understanding Realistic IVF Outcomes Is So Important 

IVF in the UK keeps growing. The HFEA, our national fertility regulator, recorded more than 77,500 IVF cycles across 52,400 patients in 2023, up from roughly 60,000 cycles a decade earlier. Around 1 in 32 UK births is now down to IVF. 

And yet the headline success rate still sits at roughly a quarter to a third per embryo transfer, depending on whether it's a fresh or frozen one. The science has improved enormously since the first IVF baby was born in 1978, yet we still haven’t made IVF a sure thing.

I didn't understand any of this when I started. I wish someone had sat me down and explained the "IVF funnel" so I’d understand that I’d lose eggs, and then embryos (if you’re fortunate enough to have any) at every stage of the process.

When I had my first egg retrieval at 35, the doctor told me we'd collected 12 mature eggs, and I genuinely thought we'd cracked it. I assumed we'd be bringing a baby home by the end of the year. That assumption, that the number of eggs collected would equate to the number of babies, was my first mistake.

IVF is, in the bluntest sense, a numbers game. Think of it as a war of attrition. Understanding the IVF Funnel can change how prepared you feel, so I’ve written the guide my husband and I wish we’d had from the get-go.

 

The IVF Funnel: Explained

Here's how the funnel works, stage by stage, with the UK data at each step:

Step 1: Egg collection

First comes egg collection, where your mature eggs are retrieved under sedation. On average, a clinic collects 10 to 20 eggs, though it can be far fewer or many more.

I waited, not very patiently, for someone to tell me the number, convinced that more had to be better. It isn't that simple. Women who respond very strongly and produce many eggs can end up with a higher proportion of immature or lower-quality ones, so quantity and quality pull in opposite directions.

There is a sweet spot. A large analysis of more than 400,000 UK cycles found the chance of a live birth climbed with the number of eggs collected up to around 15, then levelled off and eventually declined. So if your number comes in lower than you'd hoped, bear the above in mind. My honest advice: stay off the forums. I read other people's stories of their egg counts obsessively, and it made me feel like we were doomed before we'd begun.

Something worth asking your clinic: based on my ovarian reserve and protocol, roughly how many eggs do you expect to collect? Knowing that early would have saved me a lot of spiralling.

Step 2: Fertilisation

Next, the embryologist takes over. Your eggs are mixed with sperm, or injected with a single sperm if you're having ICSI, and left overnight to fertilise.

On average, roughly 8 in 10 mature eggs fertilise. That figure drops if there's a known issue with the egg or sperm. Some drop-off here is completely normal and expected.

Step 3: Embryos that reach day 5 (blastocyst)

Then the waiting starts. Over the next five to six days, the fertilised eggs grow in the lab; some will stop growing over this timeframe. In conception without IVF, a fertilised egg travels down the fallopian tube and reaches the womb around day 5 or 6 as a blastocyst, a ball of roughly 100 cells. IVF recreates that in the lab. Reaching the blastocyst stage matters because these embryos are stronger candidates for transfer and more likely to implant. 

This is where the funnel narrows most sharply. Only about 30-50% of embryos still growing on day 3 make it to the blastocyst stage, and this range varies widely with age, egg and sperm quality, and the individual lab. Many embryos simply arrest along the way. It's the most common place to lose numbers, and it isn't a reflection of anything you did.

For us IVF patients, this stage involves nothing more than waiting for the phone to ring. My clinic told me exactly when they'd call with updates, and they stuck to it, which ensured I would be at home and ready for the call, rather than flinching every time my phone buzzed. I’d recommend asking your clinic how and when they'll update you, and ask them to stick to their word. It gave me a small sense of control in a process where I actually had very little control. It astonishes me how many clinics fail at this basic task when it’s a moment in this process that causes such great anxiety for patients. 

Step 4: Embryos that are chromosomally normal

Some clinics will offer genetic testing of your embryos, known as PGT-A, which screens for the right number of chromosomes. The aim is to avoid transferring an embryo that's unlikely to lead to a healthy pregnancy, which can, in theory, shorten the time to a successful transfer and lower the chance of miscarriage.

Go in with clear eyes, though. The HFEA lists PGT-A as a treatment "add-on" and rates the evidence cautiously: for most patients, it hasn't yet been shown to improve the odds of a live birth, and it carries an extra cost and the small risk of setting aside an embryo that might have worked. It can be more useful for specific groups, such as older patients or those who've had recurrent losses. Ask your clinic why they are, or are not, recommending it for you in particular. For my IVF, we had all our embryos tested, as, for me, it wouldn’t ever make sense to take the risk of transferring a chromosomally abnormal embryo. 

How many embryos come back as normal depends heavily on age and on the egg and sperm themselves, so there's no single number to expect here.

Step 5: Transferred embryos that implant

Once you have an embryo to transfer, the two-week wait (TWW) begins. For me, it was the hardest part of the whole thing.

Some people take time off work. I did the opposite and kept busy, because sitting still with my own thoughts was my idea of hell. I booked us a few days away for the date I was due to test, with a plan for either outcome: somewhere to celebrate if the news was good, somewhere quiet to process together if it wasn't.

Clinics differ on how they test. Plenty still bring you in for a blood test, the beta hCG, while others ask you to do a home pregnancy test first and only confirm with a follow-up blood test if it's positive. On my test day, my clinic had booked bloods, but I woke up certain it hadn't worked. Over text messages, we agreed on a compromise: I'd do a home test first and go in for the beta only if it came up positive.

It’s helpful to set your expectations by understanding the "implantation rate": the share of transferred embryos that implant in the womb lining and go on to result in a confirmed pregnancy. You can ask your IVF doctor about this. 

Will my embryo implant?

Plenty of things affect whether an embryo implants, including plain luck. UK clinics report pregnancy rates per transfer of around 30 to 40% on average, rising to roughly 41% for patients aged 18 to 34 and higher again for genetically tested embryos, though the figures vary by clinic and patient. Embryo grading plays a part, too.

Grading describes how an embryo looks under the microscope: its shape and the appearance of its cells. Most systems sort embryos into good, fair, or poor. Grade isn't destiny, but it does shift the odds.

From an observational study of 1,766 single embryo transfers.

Most clinics will show you a picture of your embryo and its grade. Ask what it means for your chances. These are your potential children, and you're allowed every question you have.

Here’s my son:

Step 6: Pregnancies that become live births

About 10 to 14 days after a frozen transfer, it’s time to find out if you are pregnant. For those having a blood test to confirm (aka "beta", "beta hCG", or "β-hCG"), a beta hCG level of over 100 is generally a reassuring sign, though plenty of healthy pregnancies start lower. 

What matters more than the single number is the trend. Clinics usually repeat the test every couple of days and want to see it roughly double every 48 hours. A beta that stalls or falls is, sadly, an almost certain sign that the pregnancy isn't progressing. I loathed the phone call from the clinic that gave me my hCG result; even thinking of it now makes me feel physically sick. And that feeling was repeated days later when awaiting another call to let me know if the hCG levels had progressed as expected or not. 

A positive test doesn't guarantee a live birth, and I think it's kinder to know that going in. Research in IVF pregnancies has put the miscarriage rate at around 20%, and one clinic study of 468 day-5 single-embryo transfers found 59% led to a pregnancy but 51.7% to a live birth. There's also evidence that the early beta level itself is somewhat predictive: very low early betas are associated with a much higher risk of first-trimester loss, and high ones with a much lower risk. Other things that nudge miscarriage risk after IVF include a higher BMI and a history of previous losses.

 

Understanding your own IVF chances

No one can hand you a personal guarantee, but you can get a reasonable estimate. The CDC's IVF Success Estimator is a useful tool, though it's built on US data, so treat it as a rough guide rather than gospel for a UK cycle. The HFEA does have its own dashboard to analyse IVF data in the UK, but I don’t find it particularly user-friendly or geared towards us IVF patients. 

Your own clinic should also be able to talk you through your likely chances given your history, your test results, and their own results with patients like you. Ask them directly what their success rates are. The things that play into your chances:

• egg quality

• sperm quality

• embryo genetics and grade

• your overall health

• your medication protocol

• the reason you need IVF

• whether you've had a successful pregnancy before

• the clinic itself, including the lab and the doctor who will do your transfer.

That last point matters more than people expect. There's good evidence that the transfer technique varies between clinicians, and that a difficult transfer is linked to lower success. It's a fair thing to ask about when selecting an IVF clinic.

 

Real IVF funnels

Every funnel looks different. To show you how differently IVF can go, I want to share real numbers: my own, plus a few from women in our community who've kindly agreed to share theirs, anonymised.

Age: 35

Reason for IVF: secondary infertility

Mature eggs retrieved: 12

Fertilised: 11

Day 5: 7

Genetically normal embryos: 4

Transfers: 1 

Live Births: 1

 

Age: 37

Reason for IVF: unexplained infertility

Mature eggs retrieved: 16

Fertilised: 13

Day 5: 9

Genetically normal embryos: 3

Transfers: 3 (1 failed transfer, 2 miscarriages)

Live Births: 0

 

Age: 28

Reason for IVF: PMOS (fomerly called PCOS)

Mature eggs retrieved: 45

Fertilised: 32

Day 5: 12

Genetically normal: no PGT-A testing carried out

Transfers: 2 (1 failed transfer)

Live Births: 1 

 

Age: 39

Reason for IVF: low AMH

Mature eggs retrieved: 9

Fertilised: 7

Day 5: 5

Genetically normal: 4

Transfers: 2

Live Births: 2

 

What I learnt from my IVF 

Going through IVF is hard, financially (assuming no NHS IVF is available to you!), physically and emotionally. Find others who have gone through IVF, grill your clinic - I think we often forget we’re paying for a very expensive private healthcare treatment, and we are more than entitled to ask and expect a high level of patient care.

I spent the whole process somewhere between hoping for the best and bracing myself for the worst. I felt so much more informed when facing my second round of IVF. Knowing the funnel didn’t necessarily make the hard stages easier, but it meant I was rarely blindsided, and that turned out to be its own kind of comfort. I hope it does the same for you.

 

Key Takeaways

• IVF is a numbers game, and the numbers fall at every stage. Losing embryos along the way is normal, not failure. More eggs aren't automatically better. Around 15 is the sweet spot for a live birth. The biggest drop usually comes between day 3 and the blastocyst stage. Ending up with two good blastocysts is a genuinely decent outcome. But remember that a positive beta is the start, not the finish. Watch the trend, not the single number.

• Ask your clinic everything: expected egg numbers, how they'll update you, why they recommend any add-ons, and their own success rates.

• UK data is your best benchmark. Be wary of US figures and of comparing yourself to strangers online.