If you’re trying to get pregnant — or are just curious about how fertile you actually are — you may hear about certain tests that suggest how likely you are to conceive. One way to learn a little more about what’s going on in there is by taking a look at your ovarian follicles.
While they are by no means a crystal ball, here’s how your ovarian follicles fit into the whole process of getting pregnant and what they can tell you about your chances.
What are ovarian follicles?
Ovarian follicles are small, fluid-filled sacs in your ovaries that each contain an unfertilized egg. You’re born with a set number of eggs and ovarian follicles — usually anywhere from 1 to 2 million — and the total declines over time.
By the time you enter puberty, about 25 percent of these follicles remain, around 300,000. At menopause, fewer than 1,000 ovarian follicles are typically left.
Your follicles themselves go through various stages of development. First, primordial follicles will form in a fetus’s ovaries. They remain that way until puberty, at which point they begin to develop — just like the rest of you — and become primary follicles.
Right around the time of ovulation, some of these follicles begin to swell. One will become dominant, and the others that started growing — called antral follicles — will recede.
The dominant follicle then breaks open and releases an egg from your ovary, which travels through your fallopian tube toward the uterus. This egg will hang out for about 24 hours, creating an opportunity for fertilization to occur. The cycle continues each month until you go through menopause.
What is the antral follicle count test?
The antral follicle test is a transvaginal ultrasound that measures how many antral follicles you have. An ultrasound technician or doctor uses a probe inserted into the vagina to examine and count the number of antral follicles on the ovaries. It only takes a few minutes, similar to a pelvic exam.
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Antral follicles are very small — between 2 to 9 millimeters in diameter — but you can still see them on an ultrasound. The number of antral follicles visible can give your doctor a ballpark sense of how many total eggs (including the many follicles still too small to see) you have remaining in your ovaries.
While it’s often done on the third day of your menstrual cycle at the same time as other fertility tests, in reality it can be done at any time.
How many antral follicles are normal?
It depends on your age. If you’re older, you’ll have fewer antral follicles as someone who’s younger. On average, women in their mid 20s to early 30s have around 12 to 30 antral follicles, while women aged 35 to 40 may have between 8 and 15 and women aged 41 to 46 may have somewhere between four and 10.
If you have fewer than five antral follicles, your doctor may advise certain fertility treatments, like trying in vitro fertilization (IVF) with donor eggs.
Can you get pregnant with only one mature follicle?
If you’re trying to conceive naturally, yes, you can get pregnant as long as the follicle releases an egg down the fallopian tube to meet with sperm. But if you’re undergoing fertility treatment, it’s a little more complicated. It depends on which therapy you’re using and how old you are.
If you’re using intrauterine insemination (IUI) and you’re under the age of 40, one or two mature follicles is preferred. Having more may not significantly increase your chances of getting pregnant, but it does raise your risk of having twins or multiples if you do get pregnant, one study found.
However, women over 40 using IUI may want to consider using ovulation-stimulating treatments that will create more mature follicles. The same research found that women in this age group who had up to four mature follicles tripled their odds of pregnancy without significantly raising their chances of multiples.
If you’re undergoing IVF, your doctor will also recommend using fertility medications that produce more mature follicles, regardless of your age. You’ll receive hormone injections — usually with follicle-stimulating hormone (FSH), luteinizing hormone (LH) or both — a couple weeks beforehand to stimulate your ovaries.
During the IVF egg retrieval procedure, your doctor uses an ultrasound-guided needle to reach your ovaries and collect the egg from each follicle. Most doctors aim to retrieve more than 10 eggs per cycle.
How many immature follicles indicate polycystic ovary syndrome (PCOS)?
Women with PCOS have more antral follicles than women without PCOS. It’s not unusual for a woman with PCOS to have more than 30 antral follicles total.
Women with PCOS produce above-average levels of the hormone testosterone, which hinders ovulation. The follicles struggle to release eggs, so they hang out instead of going through the ovulation process.
You can still get pregnant with PCOS, but it may take you longer and you may need to take certain medications, such as metformin, the ovulation-inducing drug Clomid or letrozole. If these types of treatments don’t work, IVF can help make pregnancy a reality. Lifestyle changes like losing weight and boosting your vitamin D levels may also help.
The bottom line: Don’t stress too much about how many ovarian follicles you have. While they can serve as an indicator of fertility, the exact number is not the be-all and end-all.
Other factors, such as your age, weight, health history and even genetics play a role too. An antral follicle count test is one snapshot of your fertility in a moment in time, not the whole picture.
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