What Is Ovarian Reserve And How Is It Tested?

If you’ve been on the fertility journey you’ve likely heard your doctor talk about ovarian reserve. But what the heck is ovarian reserve? Honestly, it’s an educated guess of your fertility potential, based on an estimate of the number of eggs you have left!

Now there is no way to know exactly how many eggs are actually left. The markers that are used to determine ovarian reserve serve only as a proxy for egg quantity.

Ovarian reserve is a helpful tool to decipher:

who might be best suited for a visit to the reproductive endocrinologist for more advanced fertility support and when
who might over-respond to these advanced therapies, and
who might have some additional time to try and conceive on their own.

One thing ovarian reserve does not tell us is the quality of your eggs! Wouldn’t that be nice? These surrogate markers are definitely not good predictors of how great your eggs are. Big difference!! Age is still the best guesstimate we have for this, which is why at 36 we get labeled as geriatric. No lie!

I think it’s helpful to understand the natural progression of egg quantity over time. So, let’s back up a few decades to grapple with these cool details. You actually had the largest number of eggs before you were born. By 20 weeks gestation your ovaries contained somewhere between 6-7 million of these immature egg cells, but by birth that number declined to 1-2 million. By puberty, 300,000 – 400,000 remained, and by the time you hit your 30s egg count dipped to ~25,000. Pretty amazing, huh?

The point is that over time there is a natural decline in egg quantity, which diminishes ovarian reserve and thereby fertility.

So How Do I Test For Ovarian Reserve?

Unfortunately, there is limited knowledge on what controls ovarian reserve (a.k.a. the number of eggs) and how to measure it clinically. But there are a few laboratory and imaging markers that allow for a pretty good estimation.

FSH (Follicle Stimulating Hormone)

When do I test? Cycle Day 3 is the best (Cycle days 2-4 are okay). Test with Estradiol.

What is it? FSH is a hormone released by the brain that encourages ovarian egg and follicle development and maturation.

What number am I looking for? Less than 10 IU/L

If your number is higher than this, your brain is trying harder than it should to get the eggs and follicles in your ovaries to develop. Imagine this… your brain normally whispers to your eggs, but now it has to yell to get the same outcome. Your ovaries seemingly need more stimulation to do their job. This elevation could indicate that your ovarian reserve (a.k.a egg count) is declining.

There is a caveat to this. Your FSH could be less than 10 IU/L and still not be normal! What? This is complex stuff. Keep reading to understand FSH’s sister test, cycle day 3 estradiol.

Estradiol

When do I test? Cycle Day 3 is the best (Cycle days 2-4 are okay). Test with FSH.

What is it? Estradiol (a.k.a. estrogen, or at least one type of estrogen) is a hormone increasingly released from the ovaries as eggs/follicles start to develop and mature. Remember egg maturation is in response to our friend, FSH! As estradiol increases, it yells back to the brain that it can decrease the production of FSH so we don’t get too many or overripe eggs. This is called inhibition. Smart huh?

What number am I looking for? Less than 60 pg/mL

Estradiol is not a stand-alone test for ovarian reserve. It’s always ordered in combo with FSH to make sure we get a good read on both. FSH can erroneously look normal if Estradiol is too high.

AMH (Antimullerian Hormone)

When do I test? Anytime – Yay! Levels seem to stay relatively stable independent of cycle day.

What is it? AMH is a hormone produced by all the immature eggs/follicles waiting in the wings to develop. The ovaries begin producing AMH in utero at about 36 weeks gestation. Levels rise during the teen years and peak around age 25, then gradually decrease until reaching undetectable levels a few years before menopause.

AMH seems to be the most sensitive test for ovarian reserve. It is strongly correlated with the number of immature eggs/follicles, is inversely proportional to age, pretty reliably predicts how your body will respond to ovarian stimulation, and is predictive of the timing associated with the onset of menopause.

What number am I looking for? These are the general guidelines based on age. So optimally I would like to see your AMH value at or above what is listed.

25-29 years of age: 3.0 ng/mL
30-34 years of age: 2.5 ng/mL
35-39 years of age: 1.5 ng/mL
40-44 years of age: 1 ng/mL
45 years of age: 0.5 ng/mL

AMH is often used as a predictor of ovarian stimulation outcomes and helps determine dosing protocols.

AMH of 1 ng/mL to 3.5 ng/mL which is age appropriate (see above) is consistent with normal ovarian response to medicated stimulation protocols.
AMH of >3.5 ng/mL is predictive of OHSS (ovarian hyperstimulation syndrome) with ovarian stimulation. In this case medicated stimulation protocols are adapted and outcomes very closely monitored.

PCOS and AMH: An AMH of >5 ng/mL is highly diagnostic of PCOS.

Are there limitations to using AMH? YES!

There are factors that can transiently influence levels that need to be considered when interpreting AMH.

Situations that can transiently lower AMH levels:

Oral contraceptives + other medications
Systemic illness (Lupus, Chron’s, etc.)
Current pregnancy
History of ovarian surgery (think removal of endometriomas, which is ovarian endometriosis)
Endometriosis
Current smoking
Chemotherapy
Low Vitamin D level
BRCA1 carrier

Situations that can transiently increase AMH levels:

PCOS (Polycystic Ovary Syndrome) can increase AMH levels
Multiple births
Ovarian tumor

AMH is a good predictor of ovarian reserve, however, it is not a good predictor of pregnancy or bringing a baby home. You can have a low AMH and still make both of these happen, either through reproductive technologies or natural conception. So, AMH is predictive of egg quantity, but definitely not quality!

AFC (Antral Follicle Count)

When do I test? Cycle days 2-4

What is it? AFC is the sum of antral (growing but still immature) follicles visualized in both ovaries on ultrasound, that measure 2-10 mm at the beginning of your cycle, days 2-4.

What number am I looking for? A low AFC indicative of diminished ovarian reserve would be 3-4 follicles (some say 3-6), both ovaries combined.

Are there limitations to using AFC? Yes!

AFC only represents a small number of the eggs/follicles that can be visualized on ultrasound. There are other premature eggs/follicles that make up the total pool.

While a low AFC can predict a poor response to ovarian stimulation, it does not reliably predict failure to conceive

There is variability between ultrasound techs. I always recommend that this be done at a specialized fertility clinic with adequate equipment and where the techs are highly trained to obtain this particular information.

This must be done at the beginning of the cycle.

Follicular Stages Reflected by Ovarian Reserve Tests

If you’re super nerdy (like me) and want to follow along using this diagram I think it can be really helpful. If the diagram seems overwhelming, skip it! 🙂

The circles represent different stages of follicular development. The yellow circle is the egg. As the follicle develops it produces increasing amounts of estrogen, represented by the increasing thick arrows. Estradiol inhibits production of estradiol by the brain. AMH is produced by the small and large preantral follicles. In comparison, AFC pertains only to small antral follicles measuring 2-10 mm, per ovarian ultrasound. No ovarian test is reflective of the entire follicle pool.

Tal. Contemporary ovarian reserve tests. Am J Obstet Gynecol 2017.

When should I consider testing ovarian reserve?

Any sign of subfertility or infertility
- <35 years of age and trying to conceive for 12+ months
- 35+ years of age and trying to concevie for 6+ months
- 40+ years of age and trying to conceive
History of pregnancy loss
If you’re considering assisted reproductive technology, such as IVF
Polycystic Ovary Syndrome
Prior to ovarian surgery in reproductive-age women
Considering delayed pregnancy
Considering elective egg freezing
Perimenopause
Ovarian tumors
Family history of diminished ovarian reserve, premature ovarian insufficiency, premature ovarian failure
Egg donors
Prior to cancer treatment if you are of reproductive age
If you want to so you can be informed about your body and reproductive health!

How do I choose what test to do?

Once you’ve decided you need or want ovarian reserve testing, the next question is always, what test to do. There is no perfect ovarian reserve test. AMH and AFC are probably better predictors of ovarian reserve than doing an FSH/Estradiol combo. It’s definitely most convenient to do an untimed AMH. So, AMH is probably my preferred method if I had to choose one. With that said, using one marker is not ideal. I prefer a combination of these tests.

I always recommend working with your knowledgeable provider partner to get the testing that can best answer your reproductive questions to meet your goals. There is absolutely no substitute for this relationship.

You Don’t Have To Do This Alone!

If you’re thinking about getting pregnant or struggling with fertility, consider working with a holistically-minded provider who can offer a thorough assessment of your whole health and provide personalized therapeutic options. You don’t have to do this alone! 🙂

I always hope that my posts are supportive of your journey. There are additional resources and references below. Leave me a comment, check back often, and reach out if you need a partner in this process! Thanks so much for reading.

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REFERENCES

Pastore LM, Christianson MS, Stelling J, Kearns WG, Segars JH. Reproductive ovarian testing and the alphabet soup of diagnoses: DOR, POI, POF, POR, and FOR. J Assist Reprod Genet. 2018;35(1):17-23. doi:10.1007/s10815-017-1058-4
Practice Committee of the American Society for Reproductive Medicine. Testing and interpreting measures of ovarian reserve: a committee opinion. Fertil Steril. 2015 Mar;103(3):e9-e17. doi: 10.1016/j.fertnstert.2014.12.093. Epub 2015 Jan 10. PMID: 25585505.
Tal R, Seifer DB. Ovarian reserve testing: a user’s guide. Am J Obstet Gynecol. 2017 Aug;217(2):129-140. doi: 10.1016/j.ajog.2017.02.027. Epub 2017 Feb 21. PMID: 28235465

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