When we talk about ovarian reserve, we analyse the quantity of primordial follicles, structures of the ovary that store the oocytes that have yet to mature and become oocytes. The ovarian reserve refers to both the quantity and quality of the oocytes. At birth it is estimated to be between 1 and 2 million oocytes; during the onset of puberty, with the onset of menstruation, a woman will have about 400,000 oocytes; by age 37 the ovarian reserve has dropped to 25,000 oocytes, while when she reaches menopause she will have less than 1,000 oocytes. As these data show, the ovarian reserve decreases with the age of the woman, as she ages the quality and quantity of eggs decreases.
Oocyte quality is essential for female fertility, several studies show that the quality of the egg is the main responsible for obtaining an embryo of good quality, about 80%. When the ovarian reserve is diminished it causes female infertility and many complications to achieve pregnancy in a natural way.
The best way to check the oocyte quality, if they are capable of growing and developing correctly, is through an in vitro fertilization cycle, since it allows direct observation of the eggs and the embryos they produce.