USC Fertility

Antral Follicle Count

What is an antral follicle count, and how can it be used to assess fertility?

Most of our patients here at USC Fertility already know that the ovary produces the ovum, or egg, which is released from the ovary surface and drawn into the fallopian tubes during the ovulation period of a woman’s menstrual cycle.

But before the egg is released, the follicle surrounding it begins to swell. Several otherwise dormant follicles also become pronounced and begin to expand at this point; as ovulation approaches, one of these will become dominant. The rest will recede as the dominant follicle releases its egg and the cycle continues.

Prior to ovulation, these antral follicles – also called resting follicles – can be identified and counted using a transvaginal ultrasound. Since a higher number of follicles indicates a greater likelihood of fertility, USC Fertility teams typically use this procedure in conjunction with other female fertility tests to measure ovarian reserve and assess the potential for conception.

Antral follicles and ovarian reserve

Before they begin to expand and release eggs, the antral follicles are very small, about 2 to 9 millimeters in diameter, but they can be detected visually and counted. The number of antral follicles revealed by an ultrasound can indicate the number of eggs remaining in the ovary. A higher number can indicate a higher likelihood of natural conception and a higher success rate for IVF, or in vitro fertilization.

Most obgyns and reproductive endocrinologists – including the experts at USC Fertility – can establish an IVF plan and counsel patients based on the results of this test and other fertility tests that measure FSH and AMH. A higher number of antral follicles indicates likely success with the IVF process. But a low number usually indicates a poor prognosis of success, and IVF plans may need to be redirected when very low ovarian reserves are detected.

An antral follicle count in the middle of the spectrum can mean unpredictable results, and the course of action in this case may depend on a shared assessment of other factors conducted by the individual patient and physician.

Antral follicle count: How low is too low?

Counting antral follicles using an ultrasound can be a subjective process, but most fertility specialists will agree that a count of four or fewer will likely lead to poor IVF results. An ideal antral follicle count depends on the age of the woman, as 40 year old women are not expected to have the same antral follicle count as women who are 30.  A count around 20 indicates high ovarian reserve and strong chances of success, and counts higher than 30 could indicate PCOS, which won’t necessarily interfere with a healthy and successful pregnancy.  Age is the best predictor of the quality of the eggs, so the antral follicle count has to be taken into consideration with the age of the woman as both are important to predict the chance of pregnancy.

For more on the link between antral follicle count, ovarian reserve and successful conception, contact the experts at USC Fertility.