A woman’s ovarian reserve decreases with age and, with it, female fertility. A woman is born with an amount of oocytes that diminishes progressively. This is due to a process called follicular atresia. The ovaries of each woman have 750.000 oocytes at birth. From puberty, they amount for 300.000. During each period, 1000 oocytes develop. Atresia makes that only one of these oocytes, the most dominant, reaches ovulation. The rest go lost. This natural selection avoids multifetal pregnancies, uncommon in human and developed mammalians. That is why, as menstrual cycles go by, the amount of reserve oocytes subject to fertilise correctly and lead to a pregnancy decrease over the years.
However, the ovarian age of each woman does not match exactly her biological age. Same age women can have different ovarian reserves.
In order to know a woman’s ovarian reserve, namely the amount of eggs by cycle that can develop at some point, it is necessary to carry out a transvaginal ultrasound on the first days of the cycle with a Basal Antral Follicle Count (AFC) and an anti-Müllerian Hormone (AMH) analysis, that can be carried out at any time of the ovarian cycle. An abnormal value of the Anti-Müllerian hormone may be an indicator of premature ovarian failure. You can find the normal values, based on age, on some tables developed by Institut Marquès, which you can download here. Other analytic parameters to be taken into account include basal hormones (FSH, LH and Estradiol). These hormone tests are carried out on day 2 or 3 of the cycle.
If the result of these tests points out towards a low ovarian reserve, the possibilities of becoming pregnant are smaller than with a normal ovarian reserve. Hence, in order to make the wish of becoming a mother true, it is advisable to turn to assisted reproduction treatments. The specific treatment will be determined by assessing other factors, such as the male factor and the age of the patient.