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Antral Follicle Counts, Resting Follicles, Ovarian Volume and Ovarian Reserve
Testing of egg supply and predicting response to ovarian stimulation drugs
Advanced Fertility Center of Chicago
IVF and Infertility Specialists
Gurnee & Crystal Lake, Illinois
Ovarian Reserve and Egg Supply
Women are born with all of the eggs that they will ever have, and they lose them constantly throughout life until menopause, when none remain. It would be helpful to have a reliable test that would tell us 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" is useful in the field of reproductive medicine. It is an estimate of the "reserve of the woman's ovaries" - remaining egg supply - to be able to make babies in the future. In short, a woman's ovarian reserve is her remaining fertility potential.
While there are some ovarian reserve screening tests, they are far from perfect. This page is about antral follicle counts, ovarian volume and ovarian response to injectable FSH stimulation.
The ovarian reserve page has more overview information on egg quantity and quality issues, as well as other fertility screening tests.
Female age
Day 3 FSH levels
AMH blood levels
The response of the ovaries to ovarian stimulation with injectable gonadotropins is another important variable affecting chances for conception when we attempt in vitro fertilization. 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 (in conjunction with female age) are by far the best tool that we currently have for estimating ovarian reserve and/or chances for 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. So when there are only a few antral follicles visible, there are much less eggs remaining as compared to when there are more antral follicles. As women age, they have less eggs (primordial follicles) remaining, therefore they have fewer antral follicles on ultrasound.
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 are being given.
The ovary is outlined in blue. There are numerous antral follicles visible - marked with red spots.
16 are seen in this image, this ovary had a total of 35 antrals (only 1 plane is shown above)
This is a polycystic ovary, with a high antral count and volume (ovary = 37 by 19.5mm)
This woman had irregular periods and was a "high responder" to injectable FSH medication.
Normal ovarian volume and "normal" antral follicle counts
Ultrasound image of an ovary at the beginning of a menstrual cycle. No medications are being given.
The ovary is outlined in blue. 9 antral follicles are seen - marked with red spots
The ovary has normal volume (cursors measuring ovary = 30 by 17.8mm)
This woman had regular periods and a normal response to injectable FSH drugs.
Low ovarian volume and low antral follicle counts
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 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 and a cancelled cycle expected. Should consider not attempting IVF at all. Rare pregnancies if IVF attempted. |
4-7 |
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. The reduction in success rates is more pronounced beyond age 35. |
8-10 |
Reduced count. Higher than average rate of IVF cycle cancellation. Slightly reduced chances for pregnancy success as a group. |
11-14 |
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. |
15-30 |
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 than average risk for overstimulation. Very good pregnancy rate overall as a group, but some cases in the group may have egg quality issues and somewhat lower chances for pregnancy. |
Antrals and IVF Success - Female age under 35
IVF live birth rates are reduced with low antral follicle counts.
The average antral follicle count in the under 35 age group was 21.
Antrals and IVF Success - Female age 35-37
Women 35 to 37 years old have somewhat lower success than the under 35 group.
The average antral follicle count in this group was 16.
Antrals and IVF Success - Female age 38-40
The average antral follicle count at age 38 to 40 was 13.
Antrals and IVF Success - Female age 41-42
Women age 41 to 42 have substantially lower success rates.
Having more than 20 antrals was best.
However, the average antral count in this group was only 11.
All data is unpublished and from our IVF program - Advanced Fertility Center of Chicago
Risk for cycle cancellation according to the antral count
The chance of cancellation when attempting in vitro fertilization is higher with low antral follicle counts. Attempts to do IVF are sometimes "cancelled" when the ovaries respond very poorly to the stimulation meds because success rates are very low with less than 3 mature follicles.
More about IVF cycle cancellation
Learn more about antral follicle counts and response for IVF from an article review
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 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 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 injectables will 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 we sometimes get clues about the "egg quality".
For example, the eggs may demonstrate poor morphology, may have problems with maturation, or with fertilization, proper cleavage, etc.
Fertility testing in the general population
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
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