Antral Follicle Count (AFC) Can Help Predict
Reproductive Age and Treatment Response
Unlike men who produce sperm throughout their lifespan, females are born with all of their eggs. In fact, the maximum number of potential eggs, or primordial follicles are present prior to birth. At the time of birth, neonatal girls have already lost 80% of their eggs. After puberty, she will go on to ovulate approximately 400 eggs in her lifetime. This pool gradually empties and an accelerated loss begins at approximately 38 years of age with only 25,000 remaining primordial follicles which is ultimately exhausted just after menopause.
Antral follicles are a small fraction of the total primordial pool that develops in any given menstrual cycle. The number of antral follicles is a proportion of what remains in the primordial pool and can be used to estimate a woman's "reproductive age." Antral follicle counts decline with chronological age and often precedes any hormonal changes. The lower pregnancy rates seen in women during their mid to late thirties reflect this decrease in antral follicles and ultimately the number of remaining eggs. Loss occurs at every stage of life, regardless if she is pregnant or on oral contraception.
The goal of ovarian reserve testing is to determine which patients will likely respond favorably to ovarian stimulation medications that will result in a successful pregnancy. Current ovarian reserve tests include day three follicle stimulating hormone (FSH), estradiol, inhibin B and anti-mullerian hormone levels. All of these tests require a blood sample. Elevations in FSH often reflect a late manifestation of decreased ovarian reserve. A less invasive test is a measure of the basal antral follicle (AFC) count, performed by vaginal ultrasound.
To determine the AFC, each ovary is visualized by vaginal ultrasound and every follicle measuring 2-10 mm is counted. The number of small antral follicles in the ovaries is proportional to the number of remaining follicles. If <4 total follicles are measured in both ovaries, the chances of successful pregnancy is significantly reduced, even if she is undergoing in vitro fertilization (IVF). The table below illustrates the average number of AFC based on age in a fertile population.
Age |
Average AFC (each ovary) |
Range (25-75%) |
20 |
15 |
11-21 |
25 |
13 |
9-18 |
30 |
11 |
8-15 |
35 |
9 |
6-12 |
40 |
7 |
5-10 |
45 |
5 |
4-7 |
In summary, AFC performed with vaginal ultrasound is an easy and noninvasive test to help predict reproductive age and response to fertility treatment. |