Antral Follicle Counts, Resting Follicles and Ovarian Volume

Methods to help predict IVF cancellation and response to ovarian stimulation with gonadotropins

Another measure of egg quality and "ovarian reserve"

Background

It would be nice to have a reliable test to determine how good the eggs are in an individual woman at a point in time - as well as how many she still has remaining. We have some screening tests, however, they are far from perfect. This page will focus on antral follicles, ovarian size and response to injectable FSH stimulation.
There are several ways that we try to predict "egg quality" as well as trying to estimate chances for conception with various forms of treatment. Female age and "day 3 FSH" levels are 2 very important variables. The response of the ovaries to ovarian stimulation with injectable gonadotropins (FSH) is another very important variable that affects the overall chance for conception markedly when we attempt in vitro fertilization.

Antral follicles are small follicles (about 2-5 mm in diameter) that we can see (and measure) on an ultrasound of the pelvis. Antral follicles are also referred to as resting follicles. Vaginal ultrasound is the best way to accurately assess these small structures. 

Presumably, the number of antral follicles visible on ultrasound is indicative of the relative number of microscopic (and sound asleep) primordial follicles remaining in the ovary. Each primordial follicle contains an immature egg that can potentially develop in the future. In other words, when there are only a few antral follicles visible, there are less eggs remaining as compared to when there are more antral follicles visible. As women age, they have less eggs (primordial follicles) remaining, therefore they have less antral follicles.

Antral follicle counts are a good predictor of the number of mature follicles that we will be able to stimulate in the woman's ovaries when we administer the injectable

1. When there are an average (or high) number of antral follicles, we tend to get a "good" response with many mature follicles. High pregnancy rates overall.
2. When there are few antral follicles, we tend to get a poor response with few mature follicles. Cancellation of the IVD cycle is common when there are few antral follicles. Pregnancy rates are low overall in this group.
3. When the number of antral follicles is intermediate, the response is not as predictable. In most cases the response is intermediate. However, sometimes we see either a low or a very good response when there are an intermediate number of antral follicles. Pregnancy rates are pretty good overall in this group.

In at least some women, the antral follicle count may be a good predictor of the number of eggs remaining in the ovaries, as well as the quality of those eggs.

For example, we see some women in their early 20's that want to be egg donors at our center that when we do ultrasound on them we see only 3 antral follicles per ovary - and the volume of the ovary is low. Although we no longer accept these women into our egg donor program, I am not convinced that they have an egg quality or quantity problem. Often the young woman is concerned about her future fertility when we tell them that their ovaries are small and do not look like they will make sufficient eggs to be a good donor candidate. However, I am not aware of any data (medical research, etc.) that shows that women in that particular scenario are going to have a fertility problem. They might - but we just don't know. Some of those women already have 3 kids and are more fertile than they would prefer - so it is pretty hard to make the case that all women with low antral follicle counts have reduced egg quality (or quantity for that matter).

However, fertile women applying to be egg donors with few antral follicles are probably very different from women that have had difficulty conceiving. Many infertile women with low antral follicle counts do have a problem with both egg quality and quantity.

How many antral follicles is "good"?

There is not a perfect answer to this excellent question. Unfortunately, we do not live in a perfect world, and some ovaries have not yet read up on antral follicle counts to know how they are supposed to respond to stimulation. Antral follicle counts can also be somewhat "observer-dependent". This means that if we had several different trained ultrasonographers do an antral count on a woman, they would not all get exactly the same result. Therefore, what we decide looks like 6 antral follicles, at another clinic might have been read as 5 or even 8.

From our own observations and experience, here are some general guidelines:

 

Response to stimulation with gonadotropins (FSH products)

The level of response of the ovaries when the woman takes injectable FSH for stimulation is often predictive of the egg quality - and therefore, also the relative chances for success with infertility treatment.

There are no absolute and accepted cutoffs for defining "low", "normal", or "high-responders". However, here are some general guidelines:

Low responder: When stimulated aggressively with injectable FSH will develop less than 5 mature follicles - often requiring high doses of the medications. Some women will only develop 1 or 2 mature follicles - even on very high doses of the medications. These women are not good candidates for IVF using their own eggs - but are good candidates for in vitro fertilization with donor eggs.

"Normal" or "average" responder: When stimulated aggressively with injectable FSH will develop 5-8 mature follicles as well as several smaller ones.

High responder: When stimulated aggressively with injectable FSH will develop about 8 or more mature follicles as well as many more small and medium-sized follicles. These women usually respond briskly to low doses of the medications. They are also at the highest risk for ovarian hyperstimulation syndrome.

In general, normal and high-responders to stimulation have better egg quality and have significantly higher pregnancy rates with treatment.

In general, low-responders to stimulation have lower-quality eggs (as well as quantity) and have significantly lower pregnancy rates with treatment.

Other provocative tests of ovarian reserve

We can also challenge the ovaries with drugs (hormones) and assess whether they have responded appropriately in order to distinguish women with good ovarian reserve from women with diminished reserve.

For example, the exogenous FSH ovarian reserve test involves giving an FSH injection on day 3 of the cycle and testing both the baseline FSH and baseline and 24 hour post-injection estradiol to see if a normal response has resulted.

If the estradiol response is poor, ovarian reserve and egg quality are also likely to be poor. The woman is also less likely to be a "normal responder" to gonadotropin stimulation.

In vitro fertilization

This is a treatment for infertility and is never done as a "test", but at the same time it gives much useful information about egg and embryo quality. By careful examination of the eggs and embryos during the in vitro incubation process we sometimes

For example, the oocytes may demonstrate poor morphology, or may have problems with maturation, or with fertilization, proper cleavage, etc. 

Treatment options for women with low antral follicle counts and low response to stimulation

In vitro fertilization

Lupron "flare" protocol for ovarian stimulation in low responders

In vitro fertilization with assisted hatching

In vitro fertilization with donor eggs