Fertility testing 101: what is an Antral Follicle Count (AFC) and should you get one?
Updated: May 12, 2020
Before you've even decided whether or not to go through fertility treatments like egg freezing, your fertility doctor will most likely request some fertility tests. One of those key fertility tests is called your "antral follicle count" (AFC). The antral follicle count, coupled with one or more hormone blood tests, are considered the "gold standard" for fertility testing.
Here is a quick rundown of what your AFC can help indicate:
How many eggs are left in your ovaries
The total number of mature eggs you might retrieve from a stimulation cycle
The chances of one stimulation cycle resulting in a healthy baby in the future
The dosage of stimulation medication a doctor will prescribe in order to facilitate the best result
What is an antral follicle?
An antral follicle is a small, fluid-filled sac inside your ovary that contains an immature egg. The follicle itself plays a major role in egg maturation and the subsequent release of an egg in ovulation. While there are many, many follicles in the ovaries, only the antral (or mature) follicles are visible to the naked eye. It's only once your follicles reach 0.8 - 1.1cm in diameter that your doctor can measure and count the number of these antral follicles by doing an ultrasound of your ovaries. In the course of a stimulation cycle, this is about the time that your doctor would start stimulating your ovaries with hormones in order get as many as possible to reach final stages of maturation, around 1.5 - 2cm (we'll explain why that matters in a minute).
What do follicles tell you about your fertility?
Let’s dial the clock back to when you were just a baby. Back then you started out with one to two million immature follicles just sitting there dormant inside your ovaries. Once you hit puberty, that number nosedives down to around 300,000 or 400,000. By age 37, most women can expect to have about 25,000 follicles left. And when a women has around 1,000 follicles left, scientists believe that is what triggers the start of menopause.
From puberty to age 35, this translates to the loss of about 1,000 follicles per month (33 per day, on average) and the amount of follicles lost per month accelerates after age 35.
So where are those follicles going?!
Out of all of those 1,000 follicles only one has the chance of reaching ovulation. During ovulation, a mature egg is released from the follicle. The other 99% of them disintegrate back into your ovaries in a process known as atresia, which happens at various points during the maturation process. In addition to the follicles lost during your natural ovulatory cycle, there are additional outside forces like smoking that have the power to accelerate the loss of these follicles (we review all of these damaging lifestyle factors in depth in the book, Everything Egg Freezing). Because things like smoking accelerate the loss of follicles, it has the ability to accelerate aging in general, leading to cases of premature menopause.
In short, a combination of nature and nurture can will define how many follicles are left in your ovaries now (commonly referred to as your, "ovarian reserve") and how quickly they will disappear before you hit the inevitable mark of natural infertility, menopause.
DID YOU KNOW: You can carry and birth a baby even if you're going through menopause, you just have to use younger, quality eggs and have them fertilized and implanted (whether they're your own younger eggs or those received from a donor). Pretty wild, right?
Your AFC is one indication of your "ovarian reserve"
AFC is just one of the tests that can help paint a picture of how many follicles you have left in your ovaries - what's referred to as your "ovarian reserve." While this is usually accompanied by other hormonal blood tests like the anti-Müllerian hormone (AMH) to get a clearer indication on your fertility potential, it can help you understand where you are in the reproductive aging process.
It's important to note that even these biological markers are not completely accurate (e.g. your ACF count changes every month and your AMH is just one data point) and that even if your doctor says that you have a "low egg count" or "diminished ovarian reserve," THAT DOES NOT MEAN YOU CANNOT GET PREGNANT. Yes, you will probably have a harder time conceiving, and if you do, you might have a higher chance of miscarriage, but it does not mean that you are completely infertile.
After proper counseling from your doctor, having information about your existing ovarian reserve can help you understand how many fertile years you may have left, which allows you to make a more informed decision about whether or not fertility treatment like egg freezing is right for you.
Your AFC is an indication of how many eggs you might retrieve from a stimulation cycle
AFC is used as a predictor of the number of mature (or "dominant") follicles that are capable of being stimulated by the hormone injections taken before the egg retrieval takes place. And because the more eggs you have retrieved is directly correlated with an increased chance of one of them becoming a healthy baby (down the line), doctors can use the AFC to anticipate how many eggs you might get in an ovarian stimulation cycle for egg freezing or IVF.
How the AFC is performed
In order to count the number of antral follicles in your ovaries at a given time, you'll need to make an appointment at your fertility clinic where your doctor or a trained technician will perform an ultrasound. This isn't the kind of ultrasound that's often depicted on TV and movies with a wand on your tummy, this one is conducted transvaginally (we'd rather explain this upfront in order to prevent any surprises!). In this exam, a wand-like ultrasound device (called a transducer) is covered with a condom and lubrication and gently inserted into your vagina. This wand emits the ultrasound waves internally. Because it's inserted into the vagina, the images of intricate structures and processes of your ovaries and womb are clearer than they would be from an external ultrasound.
The process is quick and painless, albeit a bit awkward at first. It feels less invasive than a pap smear. You can watch on the monitor as the doctor or an ultrasound tech moves the wand left or right to get an inside view of each ovary - it's actually kind of cool to get a glimpse inside your abdomen!
"The whole vagina wand thing was kind of awkward, but it didn't hurt, and I felt quite relieved to have my doctor check my ovaries and say everything looked normal for my age." - Louise, 34
What do the AFC test results mean?
The scan cannot reveal exactly how many follicles or eggs are in your ovaries, it's a bit of a guesstimate measure based on how many the doctor can see at that particular moment in time. However, most doctors use the rule of thumb that when a woman has less than 4-5 visible follicles from the scan, that is indicative of a low ovarian reserve. What that could mean is that the ovaries may not respond well to fertility medications in an egg freezing or IVF cycle, and thus higher dosages of the stimulation medications might be necessary. Even then, multiple stimulation cycles might be needed to get a good number of eggs. This is why sometimes after a scan a doctor will say that a woman is not a "good candidate" for egg freezing or IVF: ovarian stimulation would be unlikely to work very well.
On the other side of the spectrum, women with exceptionally high antral follicle counts might be likely to have polycystic ovarian syndrome (PCOS) (this is something your doctor will discuss with you). If this is the case, lower dosages of hormones are usually required to get a good number of eggs. But because women with a high AFC are likely to be very responsive to the hormones, they are more susceptible to over-stimulation, a condition called ovarian hyperstimulation syndrome (OHSS).
If you have a normal or high AFC right now, that's great, but also be prepared that it will start to decline at a faster rate after age 35.
What should your AFC be?
This varies from woman to woman, but there are some general benchmarks.
AFC naturally falls as you get older, as this study of shows:
Age Average AFC Lowest AFC Highest AFC
25 to 34 15 3 30
35 to 40 9 1 25
41 to 46 4 1 17
Bear in mind that these are clustered age groups and the women in the study all had regular menstrual cycles and no history of fertility problems, so your own AFC results may be different.
Does a low AFC count mean you are infertile?
Your ovarian reserve does not directly indicate your likelihood of getting pregnant. It's not a zero sum game. That means the AFC can't accurately predict the likelihood of you getting pregnant if you tried to, say, next month. Fertility is a numbers game to a certain extent, but all that's needed for pregnancy is one good quality egg to be ovulated - and that can happen whether you have a store of millions or only a few hundred queueing up behind by the time you get to trying.
If you get a lower result that you were expecting, remember that a low antral follicle count does not mean that you are necessarily infertile or less likely to get pregnant in the near future than your friend with a high count. Don't throw away the condoms! (Unless you are ready for the possibility of a baby.) We've heard several stories of women who were told they had low ovarian reserve who assumed that meant they would be unlikely to conceive - one of them fell pregnant literally the month right after her doctor's appointment! It is a more of a measure of where you are on the fertility decline curve, and how many years you potentially have left to plan for a family. But remember, while it is a numbers game to some degree, when the time comes and you want to try to get pregnant, all it takes is one good quality egg to be ovulated. Although it's a useful indicator, the AFC is just ONE metric in the overall fertility picture.
How accurate is the AFC?
For all the marvels of modern medicine, most doctors admit that fertility is still kind of a mystery.
Even with today's advanced technology, there is still no one simple way to measure your full fertility potential with 100% certainty. Granted, doctors have an array of tests at their disposable that can give a good indication. But that's generally all the tests can give - an indication.
This isn't to say don't bother getting a fertility checkup with your gynecologist or at a fertility clinic - quite the opposite. In our opinion it is absolutely worth getting a professional to check out what's going on under the hood and keep on top of your reproductive health, especially if you're in your thirties or forties and not ready to start a family yet.
Get the full story in Everything Egg Freezing, the Step-by-Step Guide to Doing it Right.