Antral follicle count

Last revised by Owen Kang on 27 Jul 2022

Antral follicle count (AFC) or basal antral follicle count is a test performed to check a female individual's ovarian reserve. 

A female is born with a lifetime supply of eggs and as she enters puberty these eggs develop. During and after puberty these follicles develop and are released on a monthly basis.

An antral follicle is a resting follicle and appears as a small fluid-filled sac which contains an immature egg. These follicles can be measured and counted on cycle days 2, 3 and 5. The antral follicles vary every month.

Antral follicle count is rightly done on day 3 of the cycle by a Trans vaginal ultrasound. Initially the ovarian volume of both the ovaries is calculated. Further the number of small antral follicles in both the ovaries is measured. These follicles could vary in size from 2-10 mm.

What is considered a normal AFC varies between institutions. It is roughly considered to be about 3-8 per ovary. The AFC count is a major predictor of the ovarian reserve and could reflect the size of the remaining primordial follicle pool.

Low fertility is characterized by low numbers of oocytes and are usually associated with high follicle stimulating hormone (FSH) levels.

It is considered to be more accurate than the basal FSH testing for older women >44 years of age when predicting IVF outcome.

When an average to high number of antral follicles (eight or more) are visible on the ultrasound, fertility specialists expect to be able to retrieve an adequate number of eggs and the pregnancy rates are higher than average. If few antral follicles are evident, a poorer response is expected and the IVF cycle could be canceled to attempt better counts the following month.

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