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Women's age and its impact on fertility
Female fertility is considered to peak around the age of 25. After that, it begins to fall gradually, collapsing at around 38. After the age of 42, the chances of pregnancy are minimal. At 45, spontaneous pregnancies are exceptional. At the same time, the risk of pregnancy not reaching term increases with age. The older the mother, the greater the risk of miscarriage. For women aged 43 and over, it is therefore advisable for the patient and her doctor to assess the benefit-risk balance before starting a fertility procedure. There will be a charge for this and it will not be reimbursed by the social security system.
How does age influence female fertility?
As we have already seen, age can have a number of adverse effects on female fertility. Consequently, age also has an effect on the functioning of the female reproductive system. Scientific studies show that age influences hormone production, the immune and inflammatory response, and cell multiplication.
1. Impact of age on female fertility: oocyte quality
One of the impacts of age on female fertility is on oocyte quality. The low chances of pregnancy in women aged over 40 are associated with an alteration in oocyte quality. In fact, the risk of oocytes having an abnormal number of chromosomes and genetic mutations increases with age. This is associated with reduced production of antioxidants and increased release of mutagenic oxidative molecules.
2. Impact of age on female fertility: luteal phase abnormalities
Another impact that age can have on female fertility is on the corpus luteum during the luteal phase. After ovulation, the corpus luteum produces progesterone during the luteal phase. With age, however, it has been observed that the corpus luteum produces smaller quantities of this hormone, which plays a key role in the early stages of pregnancy (endometrial maturation, implantation of the embryo, embryonic nutrition).
3. Impact of age on female fertility: endometrial maturation
A woman's age slows down the process of cell proliferation. This is associated with an increase in cellular senescence (loss of cell function). This phenomenon is responsible for a reduction in the thickness of the endometrium, which will inevitably have an impact on female fertility. However, embryo implantation requires the endometrium to have reached optimum thickness.
4. Impact of age on female fertility: immunotolerance towards the embryo
With age, fertility, particularly the body's immune and inflammatory response, is disrupted. Yet it plays a fundamental role during pregnancy, as the mother's body has to adapt to implantation. Age disrupts the endometrium's immune response to the embryo: immunotolerance is impaired and the endometrium has difficulty accepting the embryo.
5. Impact of age on female fertility: the hormonal function of the placenta
In addition to the other impacts on female fertility that have been highlighted, it has recently been observed that the establishment of hormonal function (in particular the production of oestrogen and progesterone) is delayed in the placentas of older women. This leads to vascularisation defects at the placenta/uterus interface, which can be the cause of miscarriage.
Age, therefore, has deleterious effects on the entire female reproductive system: oocyte quality, hormone production, endometrial maturation, immunotolerance, and placental function are all altered. These effects may be responsible for reducing the chances of pregnancy and increasing the risk of miscarriage in women aged over 42.
Men's age and its impact on fertility
In men, the "fertility peak" occurs between the ages of 30 and 34. After this age, fertility begins to decline, although this drop is a lot less pronounced than that seen in women. Male fertility begins to fall significantly from the age of 45. Thus, 78% of men under 35 manage to conceive a child within 6 months. Only 58% of men over 35 succeed.
How does age influence male fertility?
1. Impact of age on male fertility: hormone production
One impact that age can have on male fertility is on hormone production. The frequency and production rates of the hormones LH and FSH released by the pituitary gland are deregulated. One of the consequences is a reduction in the number of Leydig cells in the testicle, leading to a reduction in testosterone production. This phenomenon can be observed from the age of 40.
2. Impact of age on male fertility: sperm production
Age is associated with a reduction in the number of sperm-producing Sertoli cells in the testis. These effects are associated with an increase in cell death and a decrease in cell proliferation. From the age of 50 onwards, a man produces 30% fewer sperm each day, which has a considerable impact on his fertility.
3. Impact of age on male fertility: sperm parameters
In men aged 50, a reduction in the number of sperm produced has been observed. In addition to these effects on male fertility, there is evidence of reduced mobility and changes in sperm morphology. Sperm DNA abnormalities are also common in men over the age of 40.
4. Impact of age on male fertility: benign prostatic hyperplasia
With age, the prostate increases in size, and this can have an impact on male fertility. This can be associated with a reduction in sperm volume. The prostate is involved in the production of seminal fluid, the main component of sperm. This is rich in fructose, proteins, zinc, and trace elements, which are essential for the survival of spermatozoa.
5. Impact of age on male fertility: the evolution of pregnancy
Finally, the last impact that age can have on male fertility concerns the development of pregnancy. In men over the age of 40, the fertilising power of spermatozoa is impaired. This is associated with a reduction in the number of embryos reaching the blastocyst stage. The implantation rate of embryos is also altered, and the chances of pregnancy are reduced. Contrary to popular belief, a man's age also influences a couple's fertility.
After the age of 40, the production of sex hormones, the quantity of sperm produced, and the fertilising power of spermatozoa is altered. This can reduce the chances of embryo implantation. So, although there is no such thing as "andropause or male menopause", a man's age can influence his chances of pregnancy.
