What is Ovarian Reserve?

Ovarian reserve plays a crucial role in fertility of a woman. Ovarian reserve is a term that refers to a woman’s current egg supply and seems to be closely associated with reproductive potential.

Females are born with their ovaries filled with eggs, representing the reserve for their life-time, called ovarian reserve. If all of the eggs are used or gone, no more reproductive hormones (estrogens and progesterone) will be produced and the woman will not have her period. Low ovarian reserve is when there is a physiological decrease in the number of eggs, resulting in an insufficient number to ensure a reasonable chance of pregnancy.

How is ovarian reserve assessed?

Follicle-stimulating hormone (FSH) and estradiol

Measuring the hormone level in blood, is perhaps the most common way to test the ovarian reserve. Follicle-stimulating hormone (FSH) and estradiol levels in the blood are measured at the start of the menstrual cycle(day 2 or 3). The level of these hormones show how the ovaries and the pituitary gland are working together.

FSH is produced by pituitary gland to help the follicle (small cyst which contains the egg) to grow. Generally, FSH levels are low in the beginning of the menstrual period and then rise, causing a follicle to grow and the egg to mature. In case the existing number of eggs in the ovaries is reduced, the pituitary gland produces more FSH to make the ovaries producing a follicle.

In general, it is known that women, who have high FSH levels on the day-3 of their cycle, are less likely to have a baby after either ovulation induction or in vitro fertilisation (IVF) when compared to other women of the same age with a normal ovarian reserve.

Hence, an increase of FSH levels on day-3 of the cycle occurs at the latest stage of ovarian reserve depletion. One should not focus on FSH alone for ovarian reserve testing/diagnosis. Other factors like ultrasound evaluation of the presence of follicles should be the method of choice to assess the ovarian reserve.

Anti-mullerian hormone (AMH)

Anti-mullerian hormone (AMH) is at the moment the most accurate test to assess ovarian reserve. As the Anti-Muellerian-Hormone is excreted by small follicles, that represent the number of eggs available at the time of the blood test, AMH levels accurately reflect the ovarian follicular reserve. Therefore, it can be considered as an extremely sensitive marker of ovarian aging and a valuable tool in the assessment of the ovarian reserve.

Another advantage is that AMH concentration remains more or less stable throughout the menstrual cycle, so the blood test for AMH can be performed throughout the whole cycle, even though, some differences exist between the cycle days.

A higher level of AMH concentration is associated with increased numbers of mature oocytes, embryos and clinical pregnancies during infertility treatment, but can also indicate a higher risk for developing ovarian hyperstimulation syndrome (OHSS) during IVF treatment.

Antral Follicle Count (AFC)

The Antral Follicle Count (AFC) is measured by transvaginal ultrasound in the early menstrual cycle by counting the number of small (2mm-10mm) follicles in each of the ovaries.

Those small follicles are called antral follicles. Later during the cycle some of them will grow and have mature eggs inside. The number of antral follicles can give the physician an exact idea of how many eggs are available and about the woman’s response to hormonal stimulation medications like gonadotropins.

The aim of these tests is to estimate the ovarian reserve and therefore the fertility of a woman and also help predict a woman’s response to fertility treatment.

An abnormal ovarian reserve test indicates that the fertility potential has declined. But the tests will not be able to predict whether a patient will conceive or not. Despite the many ovarian reserve tests thatare available, age remains the best predictor of pregnancy, because these tests only measure the number, but not the quality of the eggs.

The assessment of the ovarian reserve should only be done when implemented with proper counselling and these tests are integrated into the development of an individual treatment plan for the patient.

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