Understanding Fertility: A Guide to Antral Follicle Count

Antral follicles are fluid-filled sacs located on the outside of ovaries, which contain immature eggs. Each month, during the ovulation stage of the menstrual cycle, a mature follicle ruptures and releases an egg. 

The number of follicles produced in any cycle is relative, and varies from one individual to another. In this article we shall be discussing what antral follicle count is and the role it plays when it comes to assisted reproduction treatments. 

Antral Follicle Count

Antral follicle count is the measure by which an individual’s fertility is determined. It indicates a person’s ability to become pregnant naturally. Antral follicles develop and begin maturation in groups. Without any interventions, it is typical for only one of these to reach maturity per cycle.

In order to determine the viability of antral follicles, several factors are considered. These factors affect not just the number of follicles produced but also the quality. Some of the common factors are:

Age

As a person grows older, the number of follicles that their ovaries produce decreases. This reduces the likelihood that they will become pregnant at each cycle. Additionally, the quality of eggs produced tends to decline with age.

Health

An individual’s health is another factor that directly affects the viability of antral follicles. Typically tobacco, drugs, and alcohol have a negative impact. Other factors such as a person’s Body Mass Index (BMI) and lifestyle choices may also affect the number and quality of follicles produced.

Medical History

Some conditions and diseases, such as Polycystic Ovary Syndrome (PCOS), hypertension, endometriosis, chlamydia, periodontal disease, and even chemotherapy and radiation treatments, play a major role in the quantity and quality of follicles produced, sometimes causing infertility altogether. 

The Antral Follicle Count (AFC) Test

The AFC test is used to give an estimate of the number of oocytes (immature eggs) remaining in a person’s ovarian reserves. This informs decisions regarding the most suitable assisted reproduction treatment for that individual.

The test involves using a transvaginal ultrasound to capture images of the ovaries. These images are then sent to a specialist for interpretation. The procedure takes a few minutes and can be conducted by your healthcare provider.

The tests allow healthcare practitioners to not only observe the development of antral follicles but also assess how an individual’s AFC compares against normal ranges for their age and lifestyle.

Normal Vs. Abnormal AFC

A normal AFC is relative, varying from one person to another. The Fertility and Sterility Journal published a study that showed the production of antral follicles declines by almost 5% annually before a person reaches the age of 37, and that rate of decline more than doubles thereafter.

Another study published by Oxford University Press showed that persons with a higher number of antral follicles were able to produce a higher number of eggs after undergoing ovarian stimulation during assisted reproduction treatments.

In general, the range of AFC by age is shown below:

Age Range and Number of Antral Follicles

• Early 20s - Mid 30s - 12 - 30
• Ages 31 - 40 - 8 - 15 
• Ages 41 - 46 - 4 - 10

Follicles and Menstruation

Antral follicle development and maturation are key in determining if and when a person can get pregnant. The menstruation cycle begins with the follicular phase when the antral follicles begin to develop in preparation for fertilization. 

This period typically begins as soon as menstruation ends and lasts for about two weeks. Once a follicle matures, it is released, and this period is the ovulation period, which occurs about two weeks before menstruation. 

At this point the egg can be fertilized, leading to pregnancy. The exact moment of follicle maturation and release is unknown. As such it is possible for a pregnancy to occur before the ovulation phase begins.

Follicles for Fertility Treatments

Fertility treatments typically require more than the single mature follicle that is naturally produced. This is in order to increase the chances of fertilization and outcomes for healthy embryos.

In order to acquire the numbers needed for these treatments, a combination of hormonal injections as well as oral medications are prescribed. This not only stimulates the ovaries to produce more antral follicles, but it also causes more follicles to mature per cycle.

Intrauterine Insemination (IUI)

IUI treatments typically only require one mature follicle. However, during the hormone treatments, it is possible to have more than one follicle maturing. In order to be certain, another AFC test is done before the IUI treatment.

If the AFC test reveals that more than three mature follicles are present, often a healthcare provider will cancel the IUI procedure to prevent risks during pregnancy. Although the chances of multiple conception are low, multiple pregnancies have been known to occur using this treatment.

In Vitro Fertilization (IVF)

IVF treatments typically require about 10 - 15 follicles per round of treatment. The AFC results are used to assist healthcare providers in determining how to proceed with the hormonal phase of treatment.

The IVF process involves extracting mature follicles from the ovaries. Fertilization of the eggs also occurs outside the uterus. Stimulating multiple follicles also provides individuals with a larger number of follicles that can be immediately fertilized or frozen for future treatments.

In Conclusion

Antral follicles are the key to pregnancy, whether by natural conception or through assisted reproduction technologies. AFC is a reliable way to determine an individual’s fertility and likelihood of becoming pregnant. A low AFC is not necessarily a deterrent to pregnancy.

Although AFC does play a significant role in both natural and assisted reproduction, the health of the follicles is of more importance. Individuals who have healthier antral follicles to begin with, proceed to have healthy pregnancies, even with declined follicular production.       

Frequently Asked Questions (FAQs)

What is a transvaginal ultrasound?

A transvaginal ultrasound is a medical imaging procedure whereby the ultrasound wand is inserted into the vagina. This allows the pelvic cavity and organs, including the uterus, fallopian tubes, and ovaries, to be examined.

Is IVF better than IUI?

Each treatment has its benefits and risks. However, many factors determine which treatment works for different individuals. Consult your healthcare provider to determine which treatment would work best for you.

Why is my AFC low?

Different factors affect an AFC result, including age and medical history. Speak with your healthcare provider to determine which factors affect your low AFC and what course of action to take.

Can I increase my AFC?

The number of follicles your body produces is determined by many factors and is unique to you. Hormonal treatments used in assisted reproduction only increase the number of follicles that mature and not necessarily the number of follicles your body produces.