Antral Follicle Count

The ovaries produce tiny fluid-filled sacs called antral follicles within which eggs develop. The exact number of follicles that a female produces in a menstrual cycle is not known. What is known is that this number is different with each person, and gradually decreases as they age. Knowing the average number of follicles a person produces naturally is crucial to certain phases of fertility treatments. 

Antral Follicle Count

A person’s antral follicle count gives professional medical practitioners insight into the likelihood of natural conception. In a natural cycle, although antral follicles develop in groups, only one egg typically reaches maturity. It is this singular egg, each month that can be fertilized during the ovulation window. This ovulation window typically lasts about three days, and if it is missed, then a person or couple has to wait until the ovulation window of the following month to try again.  

Assisted reproduction therapies typically rely on the use of multiple mature eggs for the treatments to be successful. This is the reason why the number of follicles produced naturally matters. A higher number of follicles is likely to produce a higher number of mature eggs for retrieval following ovarian stimulation. That being said, there are some factors that influence the quantity, and even the quality of antral follicles a person produces. These in turn influence the outcomes of the treatments.

Age

Age is one factor whose impact is out of the control of even the most advanced medical technologies and treatments.  This is because humanity ages forward, and with each year the number of follicles a person produces diminishes. Not only that, the quality of antral follicles produced progressively decreases. Meaning that over time, a person’s likelihood of conceiving naturally progressively narrows.

Health

The parameters used to determine if a person is healthy, also give insight onto the health of their antral follicles.  A person’s body mass index, use of alcohol, tobacco or drugs, and their general lifestyle all contribute to the health of the antral follicles. As well, these markers contribute to the quantity of follicles any one ovary can produce. 

Medical History

A medical history that is colored by disease and conditions that have required medical intervention, has also been observed to influence the health and number of antral follicles a person produces. Sexually transmitted infections (STIs) such as chlamydia, conditions such as PolyCystic Ovary Syndrome (PCOS), hypertension, and endometriosis, as well as periodontal disease all create an environment whereby the ovaries cannot produce as many healthy follicles as it potentially could. Yet still people who have had to undergo chemotherapy or radiation treatments could potentially lose their ability to conceive altogether.

The Antral Follicle Count (AFC) Test

A female is born with all the eggs they will produce already ‘stocked’ within their ovaries.  This is why females are not fertile throughout their lifetimes. At a point, the reserve runs out. The purpose of an AFC is to determine by estimate, the number of potential eggs a person has in their ovarian reserve. Professional healthcare providers compare the results from this test with normal ranges. 

To conduct an AFC test, a healthcare provider captures images of the ovaries using a transvaginal ultrasound.  A specialist then analyses the images and interprets them for the healthcare provider. With this information, the healthcare provider is in a position to decide what course of assisted reproductive treatment is best suited to that patient’s circumstance. 

Normal Vs. Abnormal AFC

So, what is considered a normal range, and what is abnormal when it comes to antral follicle count? The studies that have been done show that the production of antral follicles in the ovaries declines by five percent each year once a person reaches 37 years old, more than doubling from there on out. As well, during assisted reproduction, people who have a high number of antral follicles prior to ovarian stimulation typically produce a higher number of eggs during ovarian stimulation.

As we mentioned earlier on, the number of follicles a person produces naturally varies. As such, at any stage of fertility, the count is determined by range. The table below illistrates this:

Follicles and Menstruation

A menstrual cycle revolves around the development, release and fertilization - or lack thereof - of a mature egg from an ovary. The follicular phase of this cycle is where it all begins. Antral follicles begin developing right after menstruation ends. They typically reach maturity, within a span of about two weeks. Usually only one egg matures during this period and when released, the remaining follicles stop developing. 

Ovulation is the phase during which the egg travels towards the uterus and for about a day or two is available for fertilization. If it is not fertilized, thereafter a person will have their period. Because it is not possible to know the exact moment a follicle matures and releases the egg within, it is possible for a person to conceive outside of the ovulation window. 

Follicles in Fertility Treatments

During the course of fertility treatment, a person will undergo ovarian stimulation using oral medications as well as hormonal injections. This enables the ovaries to do more than produce multiple follicles, these follicles are in a sense prodded, to each develop the egg within to maturity, resulting in the retrieval of multiple eggs per cycle. This process increases the chances for a person to become pregnant.

Intrauterine Insemination (IUI)

IUI treatments usually require the singular mature follicle for the treatment process. Ovarian stimulation during IUI can cause the ovary to develop more than one egg to maturity. So it is the practise to conduct an additional AFC test before beginning the IUI treatment. Multiple mature follicles could lead to multiple pregnancies. However if more than three mature follicles are discovered, the treatment cannot proceed, in order to prevent complications during the pregnancy. 

In Vitro Fertilization (IVF)

AFC results enable professional healthcare providers to make decisions about how to proceed in the ovarian stimulation phase of the treatment. They are able to determine how they will prescribe the hormonal medications and injections. At the end of ovarian stimulation, the expectation is that a good supply of eggs will be available to sustain more than one round of treatments, which uses about 10 - 15 follicles per round.       

To Conclude

Although antral follicle production is central to fertility, having low count does not mean you cannot become pregnant. The health of the follicles produced is of more importance than their numbers.