Antral Follicle Count (AFC)

What Antral Follicle Count Measures

An antral follicle is a small, fluid-filled follicle that has grown large enough to show up on ultrasound. Most studies define antral follicles as those measuring 2 to 10 mm in mean diameter.^[1] The granulosa cells lining these small growing follicles are the same cells that secrete AMH, which is why the count and the blood test tend to tell a similar story about the follicle pool.^[4] Ovarian reserve itself just means the number of oocytes remaining in the ovary.^[1]

How It's Measured

A sonographer or clinician scans both ovaries with a transvaginal ultrasound probe and adds up the visible antral follicles, usually during the early follicular phase of the cycle.^[1] An international consensus on the technique recommends probes of at least 7 MHz and describes several valid counting methods, from real-time 2D scanning to stored cine-loops and 3D datasets, with no single method clearly superior.^[3] Methods used to vary enough between clinics and studies that specialists published standardization recommendations to bring the counts into line.^[2]

Why People Track It

AFC shows up in fertility workups and IVF or egg freezing preparation, where clinics use it to plan ovarian stimulation.^[2] Each scan produces one number, and people going through treatment often collect several across cycles and sometimes across clinics. Recording each count with its date keeps the results comparable and in one place, next to the blood work that usually travels with them.

For how IVF tracking apps handle scans, labs, and cycle data together, see our guide to the best IVF tracking apps.

How Go Go Gaia Tracks It

Go Go Gaia has a follicle count log built in. After a scan, you enter the count in one tap and the app charts it on your fertility timeline, next to AMH, estradiol, and the rest of your labs. Every scan from every cycle stays in one record you can pull up at the next appointment.

What the Research Shows

The American Society for Reproductive Medicine's 2020 committee opinion draws the key line: markers of ovarian reserve are good predictors of oocyte yield after ovarian stimulation, but poor independent predictors of reproductive potential.^[1] That's the same caution that applies to AMH. AFC estimates the size of the follicle pool. It doesn't predict any individual's chance of conceiving.

A 2020 review comparing the two markers found AMH and AFC performed about equally well at predicting poor or excessive response to ovarian stimulation, with areas under the curve of 0.78 and 0.76. Both predicted pregnancy after IVF poorly, at 0.50 and 0.55, barely better than a coin flip.^[4]

As a measurement, AFC holds up reasonably well when it's done by experienced hands. The ASRM opinion notes it has low variability between cycles and high reliability between observers in experienced centers.^[1]

Related Terms

Frequently Asked Questions

Educational information based on published sources. Not medical advice. For personal concerns, please consult your doctor.

What is an antral follicle?

An antral follicle is a small, fluid-filled follicle in the ovary that has grown large enough to show up on ultrasound. Most studies define antral follicles as those measuring 2 to 10 mm across. The granulosa cells lining these small growing follicles also secrete AMH, which is why AFC and AMH tend to tell a similar story.

Does AFC predict whether someone can get pregnant?

No. The American Society for Reproductive Medicine's committee opinion states that markers of ovarian reserve are good predictors of oocyte yield after ovarian stimulation but poor independent predictors of reproductive potential. AFC estimates the size of the follicle pool, not any individual's chance of conceiving.

How do AFC and AMH relate?

They're the two main ovarian reserve markers, one counted on ultrasound and one measured in blood, and they come from the same biology. In research comparing them, AMH and AFC performed about equally well at predicting poor or excessive response to ovarian stimulation, and both predicted pregnancy after IVF poorly.