Why Fertility Decreases Over Time

The decrease in fertility over time is a phenomenon mainly linked to age or, rather, to the choice to have children often around the age of 35. Scientific studies have shown that from this age, female fertility begins to decline significantly. On average, reproductive capacity begins to decline significantly 12-13 years before the onset of menopause, although it is difficult to determine precisely when a woman enters menopause. However, it has been observed that, as early as the age of 35, women's fertility tends to decrease by 20-30% and by 50-60% around the age of 40 and then reaches almost nothing around the age of 42-43. This phenomenon is closely linked to the quality of the oocytes, rather than the mere presence of regular menstrual cycles. Many people mistakenly believe that regular ovulatory cycles are a sign of good fertility, but in reality, the quality of oocytes progressively decreases between the ages of 30 and 40. Oocyte aging is linked to a reduction in the DNA repair capacity, which compromises the quality of the oocytes. As a result, fertilization by sperm becomes more difficult.

Even when artificial insemination techniques are used, the decline in oocyte quality is a challenge: with intracytoplasmic sperm injection (ICSI) the problem of egg quality is overcome - in some cases - but this technique is not always effective, especially after a certain age range. In many cases, although a woman may produce oocytes as a result of hormonal stimulation, they are no longer able to be fertilized effectively. For this reason, in couples in which oocyte quality is compromised, the use of heterologous artificial fertilization techniques is proposed, which involves the use of gametes from a person outside the requesting couple.

Difficulties in fertilization and embryonic development are often attributed to dysfunctions in the mechanisms of oocyte maturation. Structural alterations that occur during oocyte meiosis and mitosis can impair the oocyte's ability to be fertilized properly. In addition to difficulty in conceiving, another fundamental aspect concerns the increase - with age - of the probability of miscarriage. Women trying to conceive over the age of 35 face a higher risk of miscarriage, which can be two to three times higher than younger women.

If, therefore, artificial insemination techniques make it possible to overcome these difficulties in some cases, it must be clear that the advancing age of the woman represents a significant obstacle to the possibility of procreation. Among the various options offered to couples, there is also the preservation of oocytes which allows women to "freeze" their oocytes at the time of greatest fertility, in order to be able to use them later. However, even this option does not guarantee 100% success, as the quality of cryopreserved oocytes can continue anyway - to decrease over time.