AFC stands for antral follicle count, a quick ultrasound scan that measures how many egg-containing follicles are visible in your ovaries at a given time. It’s one of the most widely used tests for assessing ovarian reserve, meaning the quantity of eggs you have remaining. The number gives fertility specialists a practical snapshot of how your ovaries are likely to respond to treatment, and it plays a role in diagnosing conditions like polycystic ovary syndrome (PCOS).
How the Scan Works
An AFC is performed using a transvaginal ultrasound probe operating at a frequency of 7 MHz or higher. The probe is inserted vaginally to get a close, high-resolution view of each ovary. The technician or doctor slowly scans from one edge of the ovary to the other, counting every fluid-filled follicle that measures between 2 and 10 millimeters in diameter. Follicles smaller than 2 mm or larger than 10 mm are excluded from the count.
The scan typically takes just a few minutes per ovary and can be done using standard two-dimensional ultrasound in real time or with stored 3D images. Real-time scanning allows the operator to press gently or shift the probe to confirm that a dark spot on the screen is actually a follicle, though this can take slightly longer and feel a bit more uncomfortable when many follicles are present.
When to Schedule the Scan
Traditionally, clinics schedule an AFC during days 1 through 6 of the menstrual cycle, the early follicular phase, because follicles are small and uniform before one begins to dominate. However, recent research shows that an AFC performed on any day of the cycle predicts ovarian response to IVF just as well. Scans done in the early follicular phase, mid-follicular phase (days 7 to 12), and even the luteal phase (day 13 onward) all showed statistically similar predictive accuracy. This means that if your clinic needs to schedule the scan at an unusual point in your cycle, the results are still clinically useful.
What the Numbers Mean by Age
There’s no single “normal” AFC that applies to everyone. The count naturally declines with age, and what matters most is how your number compares to others in your age group. Broadly, a count below the 10th percentile for your age suggests poor ovarian reserve, while a count below the 3rd percentile indicates very poor reserve.
Here are some median (50th percentile) values from age-specific data in fertile women to give you a frame of reference:
- Age 25: median AFC of about 14, with a typical range of 8 to 24
- Age 30: median AFC of about 12, with a typical range of 7 to 20
- Age 35: median AFC of about 10, with a typical range of 5 to 17
- Age 40: median AFC of about 8, with a typical range of 4 to 14
These numbers reflect both ovaries combined. A 35-year-old with an AFC of 5 would fall near the 10th percentile, flagging reduced reserve. A 30-year-old with the same count of 5 would be further below the expected range and closer to the 3rd percentile, which is more concerning. Context matters: the same raw number can mean very different things depending on your age.
Infertile women tend to have slightly lower counts at each age. For example, the median for infertile women at age 30 is closer to 10.5 compared to 12 for fertile women of the same age. The gap widens somewhat in the late 30s.
AFC and IVF Outcomes
The AFC doesn’t just estimate your egg supply in the abstract. It directly predicts how many eggs a fertility specialist can expect to retrieve during an IVF cycle. Research looking at “ovarian yield,” the ratio of eggs retrieved per antral follicle counted, found that women who achieved a live birth after their first embryo transfer had a significantly higher ratio of eggs per follicle (0.82) compared to those who did not (0.71). The ratio of mature eggs per follicle showed the same pattern and remained a significant predictor of live birth even across cumulative embryo transfers.
In practical terms, this means a higher AFC gives you more eggs to work with, more embryos to select from, and statistically better odds per cycle. It also helps your doctor calibrate the dose of ovarian stimulation medications. Too aggressive a protocol in someone with a low AFC risks poor response. Too gentle in someone with a high AFC may underperform.
How AFC Compares to the AMH Blood Test
The other major ovarian reserve test is AMH, or anti-Müllerian hormone, measured through a simple blood draw. AMH is produced by the same small follicles that the AFC scan counts, so the two tests are strongly correlated and essentially measure the same biological reality from different angles.
Head-to-head comparisons consistently show that AFC and AMH have similar predictive accuracy for both poor ovarian response and IVF outcomes. Neither test is clearly superior. AMH has the advantage of being a blood test, so it doesn’t depend on ultrasound image quality or operator skill. AFC has the advantage of giving your doctor a direct visual of your ovaries at the same time, which can reveal other relevant findings like cysts or structural issues. Most fertility clinics use both tests together to build a fuller picture.
AFC and PCOS Diagnosis
A high antral follicle count is one of the hallmarks of polycystic ovary syndrome. Under the original Rotterdam diagnostic criteria, a polycystic ovary was defined as one containing 12 or more follicles measuring 2 to 9 mm, or an ovarian volume greater than 10 cubic centimeters. As ultrasound technology has improved and resolution has increased, international guidelines have raised the threshold to 20 or more follicles per ovary when using modern high-frequency probes (8 MHz and above). This updated cutoff prevents overdiagnosis, since better imaging simply picks up more small follicles that older machines would have missed.
A high AFC on its own doesn’t confirm PCOS. The diagnosis also requires irregular periods, elevated androgens, or both. But if you’ve been told your follicle count is unusually high for your age, your doctor will likely evaluate you for PCOS as part of the workup.
What AFC Doesn’t Tell You
AFC measures egg quantity, not egg quality. A 38-year-old and a 28-year-old could have the same count of 12, but the younger woman’s eggs are statistically more likely to result in healthy embryos because chromosomal abnormalities increase with age independently of how many follicles remain. This is why age is still the single strongest predictor of fertility, and AFC is best interpreted alongside it rather than in isolation.
The count can also fluctuate slightly from cycle to cycle. A difference of two or three follicles between scans is normal variation, not a sign of rapid decline. If your AFC seems unexpectedly low on one scan, repeating it in a subsequent cycle can give a more reliable baseline. Factors like the operator’s experience, ultrasound equipment quality, and difficulty visualizing the ovaries in some body types can all influence the number recorded.