5 Markers of Fertility: Estimating egg reserve and egg quality

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Women are now having children at an older age than ever before. In fact, a statistic report published in the United States in 2017 found that birth rates were falling in every age group except for one: women in their 40s1. The study also found a record low of births in women aged 20-291!

Age, of course, has a significant impact on fertility. A woman is born with all of the eggs she will ever have, and reaches her peak fertility between 20 and 30 years old. Although we see fertility start to shift in the 30s, it isn’t until the mid-late 30s that we start to see fertility decline at a faster pace. That being said, age isn’t the only factor that impacts fertility. Every individual is unique, and some women get pregnant easily in their early 40s.

Interestingly, there are several markers that can be used to estimate your current fertility. These include assessing your egg reserve and estimating your egg quality. For women who are deciding whether or not to wait to have children, or for women who are struggling to get pregnant, assessing egg reserve and quality can help with decision-making and direct treatment if needed.

What factors impact egg reserve and egg quality?


As mentioned, age does have a large impact on egg reserve and quality. As women age, their number of eggs reduces naturally over time. Additionally, older eggs have been exposed to more oxidative stress, which causes DNA damage. This is why women who get pregnant later in life are more likely to have children with Down Syndrome. Fortunately, there are many ways to improve egg quality and minimize damage caused by oxidative stress—stay tuned for a future blog on this topic!

Diet and Lifestyle

Eggs are impacted by the environment they live in. This means that your diet and lifestyle can impact the quality of your eggs. Alcohol, tobacco, marijuana and poor diets can all impact the quality of a woman’s eggs.

Autoimmune conditions

Autoimmune conditions can also have a huge impact on egg quality. This is because autoimmune conditions are associated with widespread inflammation and immune system activation.


Thyroid gland health can also impact egg quality. Eggs rely on thyroid hormones for proper development, and women who have low functioning thyroid—also known as hypothyroidism—that is untreated can have lower egg quality for this reason.  (See the “What’s Next” section for more)


PCOS can impact egg quality because of the hormonal imbalance commonly associated with this condition. Small amounts of testosterone are needed for proper egg development, but too much testosterone, which is common in PCOS, can impair this process.


Finally, Endometriosis, which is an extremely painful condition where uterine-like tissue is found outside of the uterus—can impact fertility by causing inflammation and immune dysfunction.

How can you estimate egg quality and egg reserve?

LH, FSH, Estradiol (Day 3)

These three blood tests should be run together on Day 3 of the menstrual cycle for accurate interpretation. As egg quality goes down, FSH, LH and estradiol tend to rise early on in the cycle. This can be a sign that the body is trying harder to get the eggs to develop properly, and for ovulation to happen.

There are other reasons these markers could be high or low, so make sure to interpret results with the help of a health practitioner. LH, for example, can be high due to PCOS as well.


AMH is a hormone produced by the granulosa cells within the ovaries. AMH naturally declines as women age, so it always needs to be interpreted in relation to your age at the time the test was run. Note that AMH is a marker of the number of eggs you have, not their quality. Many women with low AMH can and do have healthy, to-term pregnancies.


The final marker, and the most accurate assessment, is an ultrasound assessment of the ovaries done between Day 2 and Day 5 of the cycle. This test looks at the number of antral follicles (fluid-filled sacs containing an immature egg) at the beginning of a cycle. Every menstrual cycle, hormones cause several primordial follicles to grow and develop into antral follicles. These are much larger and can be visualized on an ultrasound. Only 1 of the antral follicles will mature and ovulate. That said, the number of antral follicles found early in the cycle correlates to the number of eggs that are left in ovary overall 2.

Remember that one number does not define you or your fertility. These tests always need to be interpreted within the context of your entire health, and many of them can and do change from cycle to cycle, and with treatment.

Key Takeaways from this article

  • Age isn’t the only factor that impacts egg quality and egg reserve. Other factors include: diet and lifestyle, autoimmune conditions, thyroid health, and conditions such as PCOS and endometriosis
  • Egg quality and egg reserve can be estimated through several blood tests, including FSH, LH, Estradiol and AMH
  • The most accurate assessment of egg reserve is an ultrasound test called AFC (Antral Follicle Count)
  • One number does not define your fertility. These numbers always need to be interpreted within the context of your health and fertility overall

Learn more about egg quality

A list of studies and publications on egg quality referenced in this article