It would be helpful to have a test that showed how many eggs a woman has remaining at a point in time - as well as telling us about the quality of those eggs.

The term "ovarian reserve" refers to the reserve of the woman's ovaries (remaining egg supply) to be able to make babies.

Antral follicle counts by ultrasound are one of the best ovarian reserve tests that we currently have available.

Related Pages

Ovarian reserve

Day 3 FSH blood test

AMH blood test

Age and fertility

Egg quantity and quality

In vitro fertilization

IVF success rates

IVF pricing plans

IVF stimulation protocols

IVF with donor eggs

What Are Antral Follicles?

Antral follicles are small follicles (about 2-8 mm in diameter) that we can see - and measure and count - with ultrasound. Antral follicles are also referred to as resting follicles.

Vaginal ultrasound is the best way to accurately assess and count these small structures. In my opinion, the antral follicle counts (along with female age) are by far the best tool that we currently have for estimating ovarian reserve, the expected response to ovarian stimulating drugs, and the chance for successful pregnancy with in vitro fertilization.

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.

When there are only a few antral follicles visible, there are far fewer eggs remaining as compared to when there are more antrals. As women age, they have less eggs (primordial follicles) remaining and they have fewer 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 give injectable FSH medications that are used for in vitro fertilization. The number of eggs retrieved correlates with IVF success rates.

When there are an average (or high) number of antral follicles, we tend to get a "good" response with many mature follicles. We tend to get a good number of eggs at retrieval in these cases. Pregnancy rates are higher than average.
When there are few antral follicles, we tend to get a poor response with few mature follicles. Cancellation of the IVF cycle is much more common when there is a low antral count. Pregnancy rates are lower overall in this group. The reduction in success rates is more pronounced in women over 35 years old.
When the number of antral follicles is intermediate, the response is not as predictable. In most cases the response is intermediate. However, we could also have either a low or a good response when the antral counts are intermediate. Pregnancy rates are pretty good overall in this group.

More on egg quantity and quality issues and ovarian reserve

High ovarian volume and high antral follicle counts
Ultrasound image of an ovary at the beginning of a menstrual cycle. No medications being given. The ovary is outlined in blue. There are numerous antral follicles visible - marked with red. 16 are seen in this image. Ovary had a total of 35 antrals (only 1 plane is shown). This is a polycystic ovary, with a high antral count and high volume (ovary = 37 by 19.5mm) This woman had irregular periods and was a "high responder" to injectable FSH drugs.

Normal ovarian volume and "normal" antral follicle counts Normal Antral
Ultrasound image of an ovary early in the menstrual cycle. No medications being given. The ovary is outlined in blue. 9 antral follicles are seen - marked with red. The ovary has normal volume (cursors measuring ovary = 30 by 18mm). Expect a normal response to injectable FSH.

Low ovarian volume and low antral follicle counts Few Antral
An ovary is outlined in blue and is small (low volume) with only 1 antral
Her other ovary had only 2 antrals
She had regular periods and a normal day 3 FSH test
Attempts to stimulate her "sleepy" ovaries for IVF were not successful

How many antral follicles is "good"?

There is not a perfect answer to this 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 4 or 8, etc.

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

Total number of antral follicles	Expected response to injectable stimulating drugs and chances for IVF success
Less than 4	Extremely low count, very poor (or no) response to stimulation. Cycle cancellation is likely. Should consider not attempting IVF at all.
4-6	Low count, we are concerned about a possible/probable poor response to the stimulation drugs. Likely to need high doses of FSH product to stimulate ovaries adequately. Higher than average rate of IVF cycle cancellation. Lower than average pregnancy rates for those cases that make it to egg retrieval.
7-10	Reduced count. Higher than average rate of IVF cycle cancellation. Moderately reduced chances for pregnancy success as a group.
11-15	Normal (but intermediate) count, the response to drug stimulation is sometimes low, but usually adequate. Slight increased risk for IVF cycle cancellation. Pregnancy rates as a group slightly reduced compared to the "best" group.
16-30	Normal (good) antral count, should have an excellent response to ovarian stimulation. Likely to respond well to low doses of FSH product. Very low risk for IVF cycle cancellation. Some risk for ovarian overstimulation. Best pregnancy rates overall as a group.
Over 30	High count, watch for polycystic ovary type of ovarian response. Likely to have a high response to low doses of FSH product. Higher risk for overstimulation and ovarian hyperstimulation syndrome. Very good pregnancy rate overall as a group, but some cases in the group have egg quality issues and somewhat lower chances for pregnancy.

Correlation of antral counts and IVF outcomes

As shown below, there is a strong association between antral numbers and:

Ovarian response to stimulating medications
Chances for IVF success
Risk of having a cancelled cycle

In the charts below:

Live birth success rates shown in red text above orange columns
Rate of cycle cancellation before egg retrieval shown by blue columns and black text
Average number of eggs retrieved shown by purple text

Antrals and IVF Success - Female age under 35 IVF success by antral count under 35 years old
IVF live birth rates are reduced with low antral follicle counts
Women with low antral counts give fewer eggs and have higher cycle cancellation rates
The average antral follicle count in women under age 35 age was 23

Antrals and IVF Success - Women of ages 35-37 IVF success and cycle cancellation rates by antrals at age 35 to 37
Women 35 to 37 years old have somewhat lower success than the under 35 group
Higher rates of cycle cancellation are also seen
The average antral follicle count in this group was 18

Antrals and IVF Success - Female age 38-40 years
Age 39 antral counts and IVF
The average antral follicle count at age 38 to 40 was 13

Antrals and IVF Success - Female age 41-42
Female age 41-42 and IVF outcome by antral follicles
Women age 41 to 42 have substantially lower success rates
Having more than 20 antrals was best
However, the average count in this group was only 12

The above data is from our IVF program - Advanced Fertility Center of Chicago

Risk for cycle cancellation according to the antral count

As seen in the above charts, the chance of "cancellation" when attempting in vitro fertilization is higher with low antral follicle counts. IVF attempts are sometimes "cancelled" when the ovaries respond very poorly to stimulation meds. This is because success rates are very low when less than 3 mature follicles are present on ultrasound.

More about IVF cycle cancellation

Response to stimulation with gonadotropins (FSH drugs)

The level of response of the ovaries when the woman takes injectable FSH for stimulation is often predictive of the egg quantity and quality - and therefore, also the relative chances for success with infertility treatment. The level of response that we will get from ovarian stimulating drugs can be estimated in advance with antral follicle counts (see above table).

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 high drug doses. These women might not be good candidates for IVF using their own eggs. They will possibly need IVF 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 with injectables can develop about 8 or more mature follicles as well as many small and medium-sized follicles. These women usually respond briskly to lower doses of medications. They are at higher risk for ovarian hyperstimulation syndrome.

In vitro fertilization

This is a treatment for infertility and is not 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 in the laboratory we sometimes get clues about "egg quality".

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

Babies who had our help

Quick Links

Antral Follicle Counts, Resting Follicles and Ovarian Reserve Testing egg supply and predicting response to ovarian stimulation

Ovarian reserve, antral follicles and egg supply