Can we measure how many eggs a woman has left? Unfortunately we cannot. We can, however, use certain surrogate markers to make predictions on your ovarian reserve.
You are born with all the eggs you will ever have. Let’s say that your ovary is like a candy machine that’s holding all of your eggs. Each month, a group of eggs is released and one of them becomes the dominant egg (follicle) that awaits fertilization from sperm. The candy machine is not perfect. One month it might release more or less eggs than the month before. When we measure your ovarian reserve, we are actually measuring how many eggs are released from the ‘candy machine’ in the month you are tested.
We can measure ovarian reserve in two ways:
1️⃣ Antral follicle count (AFC) is measured using an ultrasound to visually count the number of egg (follicles) developing. It can tell us if you have released a low, average or high amount of eggs that month.
2️⃣ Anti-Müllerian hormone (AMH) is a hormone that is produced from the cells of the eggs that were released. A high AMH means lots of eggs were released that month. AMH levels are measured through a blood test.
Why are these two tests not perfect?
These tests can give a false sense of security in people who have high numbers, yet it can also give unnecessary worry in people who have low numbers. There can be a 30% variability in the number of eggs released each month and we don’t know the RATE of egg decline!
For example, if you are tested to have a high ovarian reserve, what we don’t know is whether or not you are also losing a high number of eggs each month with each menstrual cycle. Just like the candy in a candy machine eventually runs out, so do your eggs. If you’re only losing a small number of eggs each month, this can prolong your fertile years.
It is assumed that when you are young and have most of your eggs, the number of eggs that are released with each menstrual cycle is higher than when you get older and have less of your eggs.
There is no test that can tell us how many eggs you were born with. There is no test to check for your future fertility. You can only assess what’s going on right now, so to predict your ovarian reserve we must use one of the two surrogate markers mentioned above.
What about egg quality? Does AMH or AFC tell us about egg quality?
No. AMH and AFC are a quantitative measures that tell us about egg QUANTITY and doesn’t tell us anything about egg QUALITY. Low AMH is not correlated with a decreased likelihood of getting pregnant and is not a cause of infertility.
Are these tests even valuable?
As long as you are not obsessing about the raw individual numbers, these tests can allow us to put you into a general category of low, medium or high ovarian reserve. This can help us evaluate your options of starting a family naturally or if there is value in seeking out fertility care for egg or embryo freezing to start a family later on.
Just remember, having a low or medium ovarian reserve does NOT mean you will have a harder time getting pregnant. Only ONE of your egg (follicles) that is released each month will become the dominant follicle and it only requires one to get pregnant.
If you have problems with your period, there could be ovulatory concerns contributing to infertility, like PCOS or luteal phase defect. Ovulating and having predictable/regular menstrual cycles is the most important factor. This is where we want to focus our initial attention if you are trying to get pregnant. Talk to your healthcare provider about assessing your fertile potential, particularly if you are waiting to start a family - a full workup is invaluable!
To learn more, check out the study by Dr. Steiner et al. in JAMA 2017 doi:10.1001/jama.2017.14588
As always, feel free to reach out if you have any questions about your menstrual cycle or fertility.