Ovarian Reserve: FSH, AMH & Antral Follicles

Ovarian Reserve: FSH, AMH & Antral Follicles

When a woman begins to question her fertility, one of the first tests that an OB-GYN or an RE orders is blood work to test her ovarian reserve. By testing a woman’s ovarian reserve, doctors are able to get a better understanding of her fertility. In general, the quality and amount of eggs left declines as one gets older.

But while age can be a great indicator of fertility, biological age doesn’t always line up with one’s “fertility age.” In other words, a woman’s ovaries can be older or younger than she is. A woman can be 42 but have ovaries that appear to be working more like someone in the 30’s, or vice versa.

For unknown reasons, some women can find that their ovaries are acting older than their age, and these women will most likely experience menopause at an earlier age, than on average. That’s why it’s important for woman, even women in their twenties, to ask their doctors to test their ovarian reserve, so that they have a better understanding of their own personal fertility age.

How Do You Test Ovarian Reserve?

There are three main ways that doctors test ovarian reserve and fortunately neither ways are intrusive – they are just simple blood tests, or an ultrasound.


FSH stands for Follicle Stimulating Hormone, and it needs to be measured on day 2-3 of a woman’s cycle. This is important, because the ovaries need to be “quiet” meaning that the eggs have not begun their race that cycle, so there is not a lot of estrogen in the blood that cause inaccurate FSH numbers. When FSH is measured correctly on day 3, and the number is elevated beyond the average ranges, the doctor can get a good clue that the woman may have a low ovarian reserve. This diagnosis is helpful for a doctor to understand the strategy he will use when pursing infertility treatments.

It is important to keep in mind that FSH numbers are not constant. They can fluctuate every month. Therefore, many doctors will repeat FSH tests to get a good understanding of the results.


AMH stands for Anti-Mullerian hormone levels, and this is a blood test that, unlike FSH, gives a more constant number from month to month. This blood test measures the hormone which is produced by the cells within ovaries’ eggs. A higher number indicates a larger number of eggs, and an AMH reading of over 1 (by U.S. standards) suggests that the woman has a good ovarian reserve. Unlike FSH, this test is not time sensitive, and can be taken throughout the menstrual cycle.

Together, FSH and AMH give a doctor a good understanding of your ovarian reserve. There is one other test that a lot of RE’s use regularly to check ovarian reserve, and that test is taking a look at your antral follicles. This test, however, needs a more powerful ultrasound than OB-GYNs tend to have in their offices, which is why REs tend to test astral follicles more often.

Antral Follicles

Antral follicles, also known as resting follicles, represent all of the eggs that are viable within a woman’s ovaries each month. They are the small follicles, as small as 2mm in diameter, that an RE with a powerful ultrasound can view at the start of a woman’s menstrual cycle.

Many doctors consider a woman’s antral follicle count to be the best way to determine ovarian reserve. It represents, visually, how much of an egg supply a woman has, and can also be a good indicator of how well she will respond to drugs that stimulate the ovaries, as well as IVF success rates.

Antral follicles, however, may be difficult to count for a number of reasons, including their location, or if there is a cyst or fibroid blocking the doctor’s view. Therefore, the antral follicle count combined with FSH and AMH together all give a great understanding of a woman’s ovarian reserve.


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