A 45 yrs old women may be fertile and is able to conceive (although rare) while a 25 yrs old women is infertile and cannot conceive naturally. The above example reflects the reproductive potential of two women. The reproductive potential varies form woman to woman.
The reproductive potential of women depends on two factors:
1. The number of eggs in the ovaries (ovarian reserve)
2. The quality of eggs in the ovaries
Women are born with all the eggs that they will ever have. Eggs are formed from primordial follicles. The ovaries act as a bank for these primordial follicles. Ovarian reserve is the capacity of an ovary to provide healthy egg cells for fertilization that should result in pregnancy, and is determined by the number of these primordial follicles inside the ovary. The Ovarian reserve is highest in a developing foetus 18—22 weeks post conception. This initial size of the ovarian reserve varies from 35,000 to 2.5 million follicles in women and is strongly influenced by genetic factors.
The number of eggs starts declining even before a female is born and continues to do so after birth. By the time female approaches puberty the number of eggs has significantly declined from the amount at birth.
Every menstrual cycle about 10-20 primary follicles are stimulated to grow of which only one will achieve maturation and ovulate. The remaining immature follicles will degenerate. Therefore every menstrual cycle some of the primordial follicles are lost. As the female’s age increases the reserve keeps decreasing. This decline is much sharper after 35 yrs of age.
Although oocyte number and quality decline with age, fertility varies significantly among women of same age. Consequently a number od test involving biochemical measures, and ovarian imaging, collectively known as Ovarian Reserve Tests are carried out to help predict Ovarian Reserve or the Reproductive potential.
Therefore when a women wants to undergo fertility treatment it is important for fertility specialists to analyse both the Ovarian Reserve and quality of the eggs to result in pregnancy. Poor quality eggs reduce the success rate of the fertility treatments.
There are two ways in which we test the Ovarian Reserve:
a) AMH Test
b) Antral Follicle Count through USG TVS