The decline in female fertility is gradual and continuous, starting around the age of 32 but continuing more rapidly after the age of 37. Even for men, however, age matters.
Female fertility? It gradually but significantly decreases with age, starting around the age of 32 and particularly after the age of 37. This, in summary, is the conclusion of a joint document published in 2014 by the American College of Obstetricians and Gynecologists and the Society American Reproductive Medicine. The validity of the document, which replaces the previous version of 2008, was reiterated also in 2020. Let’s see what it says in detail.
Oocytes: what happens as we age
Over the years, the number of eggs contained in the ovaries declines due to a natural process called atresia . Suffice it to say that a female fetus, when it is still in the mother’s womb, has 6 to 7 million oocytes, which already at birth have become only 1-2 million, and then drop to around 300-500 thousand at puberty , to 25 thousand a 37 years old and around 1000 to 51 years old, which is at least the average age of onset of menopause in the United States.
The female reproductive system, what it does and how it is made: photo gallery
GO TO THE GALLERY
7PHOTO
Conception and the start of a pregnancy can seem mysterious events: to understand what happens and what may not work in cases of infertility, the first step is to start from the anatomy of the female genital system. Which, all in all, is less complex than one might think.
As we have seen, as reported by the document the female fertility decreases gradually but significantly from 32 years or so, and more rapidly after 37 years: a trend that reflects both the decrease in the quality of oocytes , either some hormonal variations , including the increase in circulating levels of FSH hormone and the decrease in those of anti-Müllerian hormone. Not only that: as we age, other disorders and conditions also increase that can have a negative effect on female fertility, including the risk of uterine myomas or endometriosis .
Sexual intercourse: they often decrease too
Characteristics of oocytes and hormonal aspects are not the only things that vary with age. In general, in fact, over the years there is also a decline in sexual activity , so it can be difficult to separate the weight of the two contributions – aging of the oocytes and reduction of sexual intercourse – to infertility. Yet a now historic study, published in the New England Journal of Medicine in 1982 , helped shed light on this point.
The study took into consideration women who had no conception problems but who, due to the infertility of her husband suffering from azoospermia, had to undergo inseminationwith donor sperm: one of the most favorable conditions for having a baby with the help of medicine, because it involves artificially combining the eggs and sperm of two substantially healthy people. Well, these women had achieved pregnancy in 74% of cases if they were under 32 , in 62% if they were between 32 and 35 and in 54% if they were over 35 .
A similar trend was observed in the data derived from embryo transfer programs after in vitro fertilizationin the United States. The percentage of cycles ending with a birth was: 41.5% in women less than 35 years of age; 31.9% in women between 35 and 37 years old; 22.1% in women between 38 and 40 years old; 12.4% between 41 and 42 years; 5% between 43 and 44 years and 1% over 44 years. At the same time, however, it was found that in women who had used oocytes donated by younger donors , as many as 51% of the transfers resulted in a full-term pregnancy with a live newborn , regardless of the age of the recipient.
The data from the Italian register on medically assisted procreation also confirm the trend. Those collected in 2017(the latest available) say that for insemination the pregnancy rate is 13.7% in women under 34 and drops to 3.4% for women aged 42 or over. The same applies to the success of treatments such as IVF or Icsi : out of one hundred cycles there were 24 pregnancies in women under 35, and only 5.7 in women over 43.
The importance of the time factor
The time factor is therefore very important: for this reason the American document concludes by stating that even if the diagnosis of actual infertility occurs only after a year of unsuccessful attempts, if the woman is over 35 it is good that she begins a diagnostic path already after six months. And immediately if you are over 40: even a few months can be too long if your age is “advanced” and there are reasons to suspect infertility.
READ ALSO:
Mom at 40? Here’s everything you need to know
Age also matters for humans
If once it was thought that age was a critical factor only for women, today we know that this is not exactly the case: even for men there is a decrease in fertility due to age : it seems that a first reduction in the quality of sperm starts as early as 35, to become significant after 40. Not only that: more and more data confirm that generally an older partner favors spontaneous abortions , and this regardless of the woman’s age.
