Ovarian Reserve

A term used to describe the number of eggs remaining in the ovaries at any given time. The reservoir of eggs dwindles from birth onwards, this drop in numbers speeds up from the mid-30s. There is no direct way of assessing a woman’s ovarian reserve. Antral Follicle Count, AMH blood test and FSH measurement can give an indirect picture of ovarian reserve

Ovarian reserve is a term used to refer to the number and quality of eggs in a person’s ovaries. It is also known as their “fertility potential”.

Women, non-binary, or transgender people with ovaries will begin life with all the egg cells they will ever have. This is their ovarian reserve, and in many cases it will also reflect the person’s ability to get pregnant. This ability, along with the ovarian reserve, declines as they get older. They will have fewer eggs due to age, going through their menstrual cycle, and sometimes pregnancies, and the quality of their remaining eggs will decrease. 

Altogether these factors mean that the older a person is, the less likely they are to achieve a successful pregnancy. The exact age it will stop being possible varies from person to person, but on average it is more difficult for a biologically female partner to conceive after the age of 35. 

The American College of Obstetricians and Gynecologists has made a record of the average number of oocytes (eggs) a person should have at various points throughout their life:

  • 20 weeks of gestation: 6 to 7 million 
  • Birth: 1 to 2 million
  • Puberty: 300,000 to 500,000
  • Around the age of 37: about 25,000
  • Around the age of 51 (the average age of menopause in the US): about 1,000

For some, the ovarian reserve will be much lower than expected for a person of their age or health. This is a condition known as “low ovarian reserve”, or “diminished ovarian reserve”, and often the eggs the person does have will also be of lower quality.

There are several different tests available to check on a person’s ovarian reserve. The two most common of these are blood tests used to determine the levels of follicle-stimulating hormone (FSH) and anti-Müllerian hormone (AMH), but you may also be offered one to check levels of oestradiol (oestrogen). A specialist may also recommend an antral follicle count, which will be conducted via an ultrasound scan.

Follicle-Stimulating Hormone (FSH) Test

For female patients, this blood test is an easy method of evaluating egg supply and ovarian function. This is possible because FSH is needed to stimulate the follicles inside the ovaries into producing eggs, as well as to help control and maintain the menstrual cycle.

Anti-Müllerian Hormone (AMH) Test

This blood test allows specialists to get an accurate reflection of a patient’s ovarian reserve. This is because more AMH is made in a female body, specifically in the follicles in the ovaries, after puberty has started. The higher the levels of AMH in the body, the more likely a patient is to have a larger ovarian reserve available.


This form of oestrogen is one of the most important. Testing levels of it in the body measures a patient’s ovarian function and evaluates the quality of their eggs.

Antral Follicle Count

This type of ultrasound scan involves using high-quality equipment to look at the number of antral follicles the patient has. This number is indicative of the number of microscopic primordial follicles remaining in the ovary, giving an estimate of how many immature eggs there are available.