Antral Follicle Count

The use of ultrasound scan to determine the number of eggs that a woman starts a cycle with. This is one of the parameters of ovarian reserve and can predict a woman’s response to stimulation drugs. Must be considered in combination with other ovarian reserve tests

An antral follicle count is a test carried out to reliably predict the number of mature follicles available in a female patient’s ovaries. The test is conducted via high-quality ultrasound equipment, and the results should be able to inform a specialist of the patient’s available egg supply for the future (their ovarian reserve). Carrying out an antral follicle count will often help to predict a patient’s chances of having successful IVF treatment in the future.

Antral Follicle Count

To understand more about what the test is counting, it is important to speak more about antral follicles. These are small follicles, about 2 to 9 millimetres in diameter, that can be seen and measured by fertility specialists. They are also often referred to as “resting” follicles.

When an ultrasound is conducted to measure antral follicle count, it will look at the number of antral follicles the patient has. This number is indicative of the number of microscopic primordial follicles remaining in the ovary. These primordial follicles all contain an immature egg, which may then develop and become a mature egg to be released during ovulation.

If the ultrasound reveals that there are only a few antral follicles visible, this indicates that there are far fewer eggs remaining, when compared to an ultrasound that shows more antral follicles remaining. As women or non-binary or transgender patients with ovaries get older, they have fewer antral follicles. This means that they also have fewer primordial follicles, and therefore fewer eggs left to potentially be released.

Knowing how many antral follicles a patient has left allows specialists to predict the number of mature follicles that they will be able to stimulate. This encourages the follicle to produce mature eggs, which may then be collected as part of an IVF cycle and fertilised outside of the patient’s body. For many, the number of eggs retrieved will correlate to the success rate of the cycle:

  • An average or a high number of antral follicles will often produce a good number of eggs when the time comes for them to be collected, and pregnancy rates tend to be higher
  • A lower number of antral follicles does not tend to produce a good number of eggs, and pregnancy rates tend to be lower overall in this group. It is also a much more pronounced reduction in patients over the age of 35
  • An intermediate number of antral follicles will usually not have a predictable response, and the results will normally be intermediate. However, it is also possible to have both good or poorer responses when the results are intermediate

We should also note that there is no one specific standard for how many antral follicles you need to be considered to have a “good” amount. Each body is different, and antral follicle counts can often be “observer-dependent”, meaning that a specialist may only be able to give an estimate based on the number of follicles they can see at the time of the ultrasound.

On average, a patient is considered to have:

  • A very high count if they are shown to have over 35 antral follicles
  • A normal, or good amount, of antral follicles if they are shown to have between 22 and 35 antral follicles
  • An intermediate, or normal amount, of antral follicles if they are shown to have between 14 and 21 antral follicles
  • A somewhat reduced amount if they are shown to have between 9 and 13 antral follicles
  • A low amount if they are shown to have between 4 and 9 antral follicles
  • An extremely low count if they have fewer than 4 antral follicles