What is “Ovarian Reserve”?

The “Ovarian Reserve” refers to the quantity of a woman’s eggs. It is used to refer to the ovaries’ capacity to provide egg cells that are capable of providing a successful pregnancy. 

We can think of the ovary as an “egg bank” containing primordial follicles from which a woman will draw throughout her reproductive life. Each primordial follicle contains an oocyte that remains dormant until an activation signal is received. 

At birth, most women have 1-2 million oocytes. Of these, usually only about 400,000 will be left when a woman reaches puberty and only 400 will mature and ovulate during her reproductive life. The rest will reach atresia, a natural process that leads to the breakdown of the follicle.

However, ovarian reserve does not paint the whole picture about fertility, as it doesn’t provide information about egg quality. 

Ovarian reserve estimation model according to age of Wallace and Kelsey. Retrieved from: https://doi.org/10.1371/journal.pone.0008772.g004
Ovarian reserve estimation model according to age of Wallace and Kelsey. Retrieved from: https://doi.org/10.1371/journal.pone.0008772.g004

Why does Ovarian Reserve decline?

There are several factors contributing to the decline of the Ovarian Reserve. The most obvious one is that  women are born with all the eggs that they have and they will not produce more eggs during their life. For each menstrual cycle, one follicle is selected, and the egg that it contains is released by ovulation. But for each egg cell released by ovulation, there is a larger number of follicles recruited towards maturation, which are lost to atresia. This means that each menstrual cycle leads to a loss of all eggs  recruited that month, not just the one released by ovulation.

There is a natural decline of egg quantity with age, as well as egg quality. This decline is more important after the age of 35 years old. 

What influences my Ovarian Reserve?

One’s ovarian reserve is mainly influenced by genetics. Additionally, elevated androgen levels during one’s own prenatal development – that is a certain hormone to which a baby is exposed during pregnancy – can have an adverse effect on the initial ovarian reserve.  

Ovarian reserve is naturally reduced with age as a woman loses several eggs per month during the menstrual cycle (all the eggs that have been recruited, in the process mentioned above). 

Other factors that influence the ovarian reserve can be related to one’s lifestyle, such as smoking habits, or certain medical treatments such as radiation for cancer or ovarian surgery.

How can I figure out my Ovarian Reserve?

There are two tests from which your ovarian reserve can be estimated. 

The first is the Anti-Müllerian Hormone (AMH) test. The Anti-Müllerian Hormone is produced by the granulosa cells that surround the follicles in the woman’s ovary. The higher the number of follicles in the ovary, the higher the AMH. Hence, we measure this hormone to estimate the ovarian reserve. 

The second is Antral Follicle Count. A transvaginal ultrasound can help doctors see, count and measure the Antral Follicles. The number of antral follicles counted allows us to estimate the number of immature eggs, a proxy to help estimate the ovarian reserve of the woman.