Unlike men, which can produce sperm throughout their adult life, women are born with a finite number of eggs.
At birth, girls have between one and two millions of eggs. By puberty, only approximately 400,000 of those eggs are left and most of the eggs will continue to die while they get older. It is estimated that during the female reproductive life, ovulation accounts only for about 450 eggs, while the rest of the eggs are naturally lost.
Most women are more fertile during their 20’s and start having more difficulties to conceive by their mid thirties, primarily because the number of eggs decrease with age. At approximately age 40, there is a further acceleration of egg loss, and pregnancy is even more difficult to achieve than in the mid 30s. By mid 40s, the chances of pregnancy are drastically reduced.
However, time does not only decrease the number of eggs available, it also affects the quality of eggs, which refers to how ready the eggs are to be fertilized.
Women who cannot conceive naturally and/or are planning to use assisted reproductive technologies to achieve pregnancy usually need to undergo ovarian reserve testing to assess both the quality and quantity of eggs present in their ovaries. This evaluation is done by: