A woman is born with a finite number of eggs. With age, the egg quantity and quality declines progressively from 2 million eggs at birth to 4,00,000 at puberty and further with every cycle until the time she reaches menopause.

This decline is gradual until her early 30s but increases rapidly after her mid-30s when egg reserve is 25000, out of this only around 400 are available for ovulation in the reproductive span, rest undergo atresia. This decline in ovarian reserve with time and age is irreversible. The quantity and quality of eggs is influenced by age, genetics and environmental variables.

Also, older eggs have more chromosomal i.e. genetic abnormalities which can give rise to abnormal pregnancy. Thus, with age, fertility keeps declining and miscarriage rate keeps increasing.

There are tests which detect the ovarian egg reserve of a woman and can give an idea about her fertility potential. There are two types of tests:

• Blood tests for certain hormonal levels- FSH, Estradiol, AMH
• USG imaging of the ovaries for follicular count

Follicles are like cysts inside the ovaries and they contain the egg. The pituitary gland releases FSH which causes follicular growth. In one menstrual cycle one follicle usually grows under the effect of the rising FSH levels during the cycle. This follicle releases estradiol while growing. The estradiol gives feedback to the pituitary gland in the brain to release less FSH.

Blood tests: FSH, Estradiol, AMH: To test ovarian reserve we can measure hormone blood levels .
Follicle-stimulating hormone (FSH) and estradiol are checked at the beginning of the menstrual cycle. This is usually done on cycle day 3, but it can be drawn from day 1 to 5. These hormone levels can show important information about how the ovaries and pituitary gland are working together. Serum estradiol value helps in the correct interpretation of the basal FSH values. Woman with high levels of D3 FSH / estradiol have reduced chances of conceiving with ovulation induction or IVF.
Anti-müllerian hormone (AMH) test can also tell us about the ovarian reserve. It is secreted by the early follicles and correlates well with the number of eggs in the ovaries. The advantage is that it can be measured on any day of the cycle. The main limitation is assay variability and lack of a standardized assay.

Ultrasound Imaging: Antral follicle count ( AFC)
Antral follicles are small 2-10 mm follicles in the ovaries seen at the beginning of the cycle with the help of transvaginal ultrasound scan. These follicles are cysts where the eggs develop and mature. The total number of antral follicles of both the ovaries is the antral follicle count and it gives us an idea of the number of eggs available. The accuracy of this test depends on the expertise of the observer. The quantity of eggs also tells us how a woman will respond to the ovulation drugs and gonadotropins during stimulation. Gonadotropins are hormonal medications which are administered as injections for ovarian stimulation so that multiple eggs can grow during a cycle to increase the chances of pregnancy or as a part of IVF cycle

• The purpose of using ORT as a screening test is to identify women at risk for a diminished ovarian reserve (DOR), who are more likely to have a poor response to gonadotropin stimulation and less likely to achieve a pregnancy with ART or ovulation induction. The response to fertility medications can be predicted with the help of these tests. The response is variable depending on the egg reserve in women of the same age. The fertility potential is said to have decreased in low ovarian reserve but it does not rule out the possibility of conceiving. The quality of eggs is more vital to conceiving than the quantity of eggs. Age of the woman is the primary determining factor for the quality of eggs. Women above 35 years of age have decreased fertility potential due to decreased quality of eggs (older eggs) and declining ovarian reserve. Thus, donor egg IVF may be a better option for women at advanced age groups. ORT helps to detect the decline at an early enough stage so that timely interventions could be advised.
• It also helps by making ovarian stimulation and ovulation induction safer by identifying those at risk of hyperstimulation (OHSS) prior to receiving the treatment.
• They also help and guide us in developing the best treatment protocol for women.
• No particular test of ovarian reserve can be used in isolation to predict fertility. AMH and AFC together can best predict a woman’s fertility. These tests are poor predictors of egg quality for which Age is still the best predictor.

These tests can’t tell us the chances of getting pregnant because ORT does not tell us about the egg quality or how normal and healthy the eggs are. The percentage of normal eggs we have is related to age. When we’re under 35, most of our eggs will likely be healthy. As we get older and eggs become abnormal, there are fewer normal eggs available to choose from.