Understanding Ovarian Reserve: What role does it play in your Fertility?

If you’re on a fertility journey, chances are that you’ve thought/worried/researched/stressed about your egg count or ovarian reserve. And while low (or diminished) ovarian reserve can sound scary, it doesn’t necessarily mean you’ll have trouble conceiving. It actually may mean NOTHING about your ability to conceive...

What is Ovarian Reserve? 

Ovarian reserve refers to the number of follicles (eggs) remaining in the ovaries. Women are born with a large pool or reserve of follicles that declines over their lifetime. From this pool, a certain number get recruited each cycle to continue developing, and one lucky egg gets ovulated.

You may have heard that women are born with ALL the eggs they’ll ever have. This is true, and the reproductive potential of the ovary is established before birth. We have the highest ovarian reserve at 5 months gestational age (yes, before we’re born), with a large decline to puberty and again through our reproductive years to menopause.  

The decline in egg count goes something like this:

At 5 months Gestation – ~5 million

Birth - ~1 Million

Puberty - 300,000-400,000

Reproductive Years

• Around 30 – 120 000 (12% of initial reserve)

• Around 37 – 25 000 (3% of initial reserve)
  

• Non-linear decline from 37 to menopause
  

At the onset of menopause, there are approximately 1000 eggs left (<0.1% of initial reserve).

As you can see, age is a strong predictor of egg count and it’s the most common reason for a diminished or low ovarian reserve.

Assessing Ovarian Reserve

There are 3 simple tests that we can run to check on egg count. These ovarian reserve tests look at the number of follicles that have been recruited for that cycle, also known as the “functional ovarian reserve”. This gives us insight into the remaining ovarian reserve (the total “pool”).

Functional reserve is a good indicator of total ovarian reserve because we release a consistent number of eggs each month. The amount released is relative to the total remaining number of eggs in the reserve or pool. For example, you release 10 eggs each cycle vs. 40 this cycle, 5 the next, 25 the cycle after that, etc. Functional ovarian reserve will predictably decrease with age, as our total ovarian reserve declines.

1.   Cycle Day 3 FSH

FSH or Follicle Stimulating Hormone, does exactly what the name suggests, it stimulates follicle development at the ovaries. More specifically, FSH is secreted from the pituitary gland of the brain, to act at the ovaries to promote follicular growth

FSH is mostly commonly measured in the serum (or blood) and we want FSH to be tested in the early part of the menstrual cycle (ideally cycle day 3, but cycle days 2-5 is fine). Elevated FSH >10IU/L, is a marker for reduced ovarian reserve and is a helpful tool for decision-making on how soon to see a doctor on your fertility journey.

2.     Anti-Mullerian Hormone or AMH.

I bet that you’ve heard of this one. It’s the most common test we hear about for assessing “egg count”. And for good reason! It’s a simple blood that is an excellent marker of ovarian reserve. AMH is a hormone secreted by developing follicles, the greater the number of follicles developing that cycle the higher the AMH and vice versa. Anti-Mullerian Hormone is consistent over the menstrual cycle and does not need to be tested on a specific day (unlike FSH). In women under 40, AMH does not predict the chances of natural conception per cycle or live birth rates once pregnancy is achieved. However, it is an important predictor of IVF success and response to ovarian stimulation.

AMH naturally decreases as we age, and younger women (<35 years old) with an AMH <1.0ng/mL should have further investigations for low ovarian reserve.

In general: 

• AMH >2.0ng/mL has a good prognosis for pregnancy
  

• AMH 1.0-1.9ng/mL is indeterminate

• AMH <1.0ng/mL has a poorer prognosis.

3.     Antral Follicle Count (AFC)

The 3rd way to assess ovarian reserve is by looking at the ovaries! A transvaginal ultrasound is used to visualize the ovaries and the follicles that have been recruited for that cycle (antral follicles). These follicles are then counted, and the total number observed in both ovaries gives us the antral follicle count. This is an investigation typically only performed at fertility clinics or by reproductive endocrinologists.

Understanding Diminished Ovarian Reserve

Diminished ovarian reserve (DOR) is also known as “low egg count” or low ovarian reserve. Women with low ovarian reserve may experience symptoms like irregular menstrual cycles, difficulty conceiving, or early menopause onset.

Diminished ovarian reserve can be diagnosed when the ovarian reserve tests are out of range:

1.     FSH >10IU/L

2.     AMH <0.7-1.0ng/mL

3.     Antral Follicle Count <6-10

Remember, diminished ovarian reserve is a natural phenomenon that occurs as we age, and increased age is the most common ‘cause’ of DOR. When a diminished ovarian reserve is identified in younger women (<35), we need to rule out things like infection, trauma or surgery to the ovaries, history of chemotherapy/radiation, endometriosis or autoimmune conditions that may have contributed to the low ovarian reserve.

Improving Ovarian Reserve

If your low ovarian reserve is caused by a modifiable risk factor, like smoking, environmental exposures or vitamin D deficiency, we can see an improvement or stabilization in AMH and other functional ovarian reserve markers when these are corrected. However, ovarian reserve itself cannot change and will predictably decrease with age.

While it may not be possible to increase ovarian reserve, we certainly can improve our egg quality! Ovarian reserve tests do not provide information on the quality of the eggs (only the quantity), and this is an area where our diet, lifestyle and supplement habits can have a serious positive impact.

When it comes to supplements here are the heavy hitters for egg quality:

1/ CoQ10 – supporting the energy centre of the egg.

Coenzyme Q10 is an important factor in energy production in every cell of the body, including our eggs. Our eggs use a lot of energy and often require extra support, especially as we age. After around 30 y/o, CoQ10 naturally starts to decline making CoQ10 an important supplement when trying to conceive in our 30’s and beyond. CoQ10 is also a potent antioxidant, protecting the eggs from cellular damage and protecting our ovaries.  

2/ NAC – a potent precursor to glutathione

N-acetyl cysteine is a precursor to the master antioxidant in the body, glutathione. One of the main reasons we see a decrease in egg quality is an imbalance between antioxidants and pro-oxidants. High levels of pro-oxidants cause cellular damage and aging, including eggs! NAC supplementation not only improves antioxidant status it also directly improves the quality of eggs (especially in PCOS and endometriosis).

3/ Melatonin – yes, the sleep hormone.

But it’s for so much more than that! Melatonin is a potent antioxidant, helping to protect the developing eggs from damage. It also helps to regulate FSH and LH secretion, supporting healthy egg development and ovulation.

4/ Vitamin D – The sunshine vitamin.

This is an area we want to test and treat! We know that serum vitamin D levels ≥ 100nmol/L are protective for AMH and vitamin D deficiency <75nmol/L is associated with reduced AMH. But when we supplement with Vitamin D to improve our blood levels of vitamin D, AMH and Antral Follicle Counts improve.

Getting Pregnant with Diminished Ovarian Reserve

While ovarian reserve can serve as a valuable diagnostic tool, it doesn't determine egg quality or conception timelines, especially for women under 40. Empower yourself by focusing on aspects within your control and taking proactive steps towards parenthood.

Your journey to parenthood is unique, let's navigate this journey together, empowering you to realize your dreams of building a family.