A woman's ovarian reserve is made up of all the primary follicles in her ovaries. These are structures that store the oocytes and that, with time, can mature and give rise to mature eggs. The ovarian reserve refers to both the quantity and quality of the oocytes.
At birth it is estimated that the woman has an ovarian reserve of between 1 and 2 million oocytes. However, at the beginning of puberty when the first menstruation begins, this ovarian reserve will already have been reduced to 500,000 oocytes.
Over the years, a woman's ovarian reserve will gradually decrease until she reaches menopause. As these data show, the ovarian reserve decreases with the woman's age, both in quantity and quality.