Two of the first IVF-related events you’ll experience are the “day 3 baseline scans” and the “antral follicle count”. (Find out more about IVF prep and tests here.) But what is the antral follicle count, and what does it measure? All will be revealed after this quick warning:
The quick warning:
There’ll be a lot of paperwork and a number of exhaustive (as well as exhausting) appointments before you have any blood tests or scans. By the time you’re in stirrups and about to get your antral follicle count assessed, there’s a good chance you’ll no longer care why. But it’s important to understand the results, because they’ll have implications for the rest of your treatment.
What are antral follicles?
They’re small egg-containing follicles (about 2–9 mm in diameter) that can be seen, measured and counted with ultrasound. They’re also referred to as “resting” follicles because they’re the ones that are primed to grow, ready for ovulation, in this particular menstrual cycle.
You also have heaps and heaps of other, “microscopic follicles”. These lie quietly for months or even years at a time, and at some point they’ll be part of the “chosen few” that become antral follicles.
What does the “antral follicle count” involve?
The antral follicle count is a transvaginal ultrasound examination (the first of many) that counts how many antral follicles you have in your ovaries.
You’ll also have blood tests for FSH, AMH and oestradiol levels, which attempt to discover the same thing. (You have a bunch of different tests rather than just one in case there’s a misleading or dodgy result.)
Why does it matter how many antral follicles there are?
The number of antral follicles visible on the ultrasound provides a good indicator of the total number of all follicles you have at your disposal. That is, if you have a decent number of antral follicles, it means you probably have a decent number of microscopic follicles too.
So again… why does this matter?
It matters if you don’t have a decent number of antral follicles, because it suggests you don’t have too many microscopic follicles either. That, in turn, means there’s less chance that you’ll conceive – because you have far fewer egg-containing follicles where the egg could potentially become fertilised.
A low egg count is normally associated with age: the older you are, the fewer eggs you’ll have. What’s more, you start to lose eggs at a much faster rate as you get older – it’s not like you consistently lose the same number of eggs every month throughout your life.
Age also contributes to lower-quality eggs – and low-quality eggs are far less likely to fertilise, implant or carry to term without miscarriage. If you’re over the age of 35 and the antral follicle count shows that your egg supply is dwindling, it’s also likely that many of those remaining eggs are lower quality.
This makes it harder for you to conceive naturally, but it also makes it tougher for you to conceive via IVF. Why? Because with IVF, it’s beneficial to produce as many follicles as possible per cycle. (See the article on the IVF process for more on this.) If you don’t have many follicles in the first place, it’ll be harder for you to produce the metric ton of them that they like to get out of you.
My antral follicle count is low. Should I get fertility treatment or try to conceive naturally?
If your antral follicle count is low, the other tests mentioned earlier (AMH, oestradiol and FSH) will confirm that you’re definitely lacking in the egg department.
But not everyone with a low egg supply needs fertility treatment – at least, not if they’re under the age of 35. Why? Because, with a natural cycle, you only release one egg a month anyway: you don’t have to magic up a bunch of eggs per cycle like you do with IVF. What’s more, the quality of your eggs is likely to be good (egg quality also decreases with age).
Having said that, you’re here, reading this paragraph – and you already know your antral follicle count. That suggests you’ve probably already tried and struggled to conceive naturally, and you’ve decided that fertility treatment is the way forward. The next section goes into more detail about why you have a good chance of success.
If you’re over the age of 35, your egg supply matters a lot more – whether you’re undergoing fertility treatment or not. That’s because the quality of your eggs is also likely to be compromised, which means it’s less likely that natural conception or fertility treatment will work as well for you. As a result, it probably will be much harder to get pregnant. Here’s more information about how egg quality and egg quantity matter when it comes to conception. While fertility treatment can definitely still work (and plenty of people have had success with it), bear it mind that it will probably be harder to conceive.
Keep reading… there's more below.
My antral follicle count is low AND I definitely can’t conceive naturally! Am I a lost cause for IVF?
If you’re young, you have a low antral follicle count and you can’t get pregnant, it’s definitely worth trying IVF because you probably still have fabulous-quality eggs – and successful fertilisation and implantation relies on good-quality eggs.
It’s for this reason that the vast majority of clinics and hospitals will still treat you if you have a low antral follicle count (although it can’t be too low – see below). They may well put you on a more aggressive IVF protocol to make sure you produce as many follicles as you possibly can, but that’s about the only difference.
(If it turns out you have low-quality eggs too, despite being relatively young, there are a few things you can potentially do to improve them. Read more about how egg quality can be measured – and how you can improve it if necessary.)
If you’re over the age of 35, things get trickier: it’s likely that you no longer have high-quality eggs, and IVF is therefore less likely to be successful. BUT plenty of people in your situation have undergone successful IVF treatment, and it could happen to you too. Bear in mind that many clinics and hospitals have age cutoffs for treatment, though. If you’re no longer eligible for IVF treatment using your own eggs, you could consider donor eggs or embryos.
It’s also important to remember that while you can’t increase your egg count, you can improve the quality of your eggs. This article explores some of the ways in which you can do it.
How many antral follicles is considered “good”?
There isn’t a definitive answer to this question, but here are some generally agreed-upon guidelines:
- Extremely low count (consider cancelling IVF – even for people who are young – because response to ovarian stimulation will be very low): less than 4 antral follicles detected
- Low count (will probably require an aggressive IVF protocol): 4–9 antral follicles detected
- Slightly reduced count (not great but not disastrous for younger women): 9–13 antral follicles detected
- Almost normal count: 14–21 antral follicles detected
- Normal count (should respond fabulously to ovarian stimulation medication – although at slight risk of ovarian hyperstimulation): 22–35 antral follicles detected
- Very high count (possibly has PCOS and is at high risk of ovarian hyperstimulation BUT has a great chance of responding well to ovarian stimulation): over 35 antral follicles detected
Note: the National Institute for Health and Care Excellence (NICE) specifies that “less than or equal to 4” will lead to a “low response”, and “greater than 16” will lead to a “high response”.
One thing to bear in mind is that antral follicle counts are “observer dependent”: two doctors may well reach different results. It’s one of a few reasons to combine the antral follicle count with other egg-quantity measurements before starting IVF.
The antral follicle count: bloomin’ useful but not perfect
The “observer dependedness” of the antral follicle count means it should be taken with a pinch of salt – or, more usefully, performed alongside other tests that can help to confirm a low egg supply. But there’s no denying that it’s an incredibly useful predictor of IVF success – and how easy/difficult it will be to reach that success.