What is ovarian reserve?
Ovarian reserve refers to the total number of follicles present in the ovaries at any given time. A follicle is a small fluid-filled sac, measuring between 2 to 10mm, which contains an egg. Therefore ovarian reserve represents a quantitative method, to measure the number of eggs left in the ovaries.
How age affects ovarian reserve?
The number of eggs in women declines irreversibly and continuously throughout life. Women are born with approximately 2 million eggs in their ovaries. At puberty the number of eggs is roughly 400,000 and continue to decrease throughout reproductive life. Usually this reduction becomes more intense about 10 years prior to the menopause, when the number of remaining eggs is just a few hundreds.
However, the age by which this significant drop in the quantity of the remaining eggs will occur varies considerably amongst women. Women with a small number of remaining eggs have a low ovarian reserve and this could affect their reproductive outcomes.
How is ovarian reserve assessed?
There are tests known as markers, to assess the ovarian reserve.
For an accurate assessment of the ovarian reserve, a combination of the following two tests is recommended:
- Measurement of the levels of Anti-Mullerian Hormone (AMH), which is a blood test.
- Measurement of the Antral Follicle Count (AFC), which is done through a pelvic ultrasound scan.
Anti-Mullerian Hormone (AMH)
Anti-Mullerian Hormone (AMH) is a hormone produced by the ovarian follicles. Therefore, AMH levels in the blood are directly correlated to the number of the follicles, indicating the number of eggs available in the ovaries.
AMH levels decline with age, while high levels of AMH can suggest polycystic ovaries.
Measurement of the AMH level is considered the most accurate blood test for the assessment of the ovarian reserve and can be done at any point in the menstrual cycle.
Antral Follicle Count (AFC)
Antral follicle count (AFC) is the number of the small follicles, measuring between 2 to 10mm, present in the ovaries. They are measured at the beginning of the menstrual cycle through vaginal ultrasound examination. An AFC of less than 5 suggests a low ovarian reserve.
Why is ovarian reserve assessment important?
Egg quantity has been associated with the chances of a woman getting pregnant either naturally or through an IVF treatment. An accurate assessment of the ovarian reserve is therefore essential, as it helps determine the fertility potential in women.
Particularly for women undergoing IVF treatment, precise assessment of the ovarian reserve, helps to determine the appropriate dose of medication required for optimal response of the ovaries. Furthermore for women with polycystic ovaries undergoing IVF treatment, accurate information regarding the number of follicles in the ovaries can help to reduce the risk of hyper-stimulation.