Number of children, age of pregnancy: what impact on women’s longevity?

We know that the longer women wait to have children, the more likely they are to face difficulties conceiving. However, for those who have the possibility of having children later without medical assistance, it seems that their “luck” is twofold: this ability would be the sign of a well-preserved biology.

Giving birth after age 33: a factor associated with greater longevity

A study published in the journal Menopause reports that women who have a child naturally after age 33 also have a longer life expectancy than women who have their child before age 30 (1).

Read: Questions you ask yourself about fertility

A previous study showed that women who gave birth to a child after the age of 40 were 4 times more likely to become centenarians than women who had their child earlier. Many other studies have shown an association between having children later and a longer lifespan.

In this new study, researchers analyzed data from 462 women who were part of the Long Life Family Studya genetic study of a population with exceptional longevity (4875 participants belonging to 551 families in the United States and Denmark). They separated the 462 women into two groups: 311 women who lived to be 95 years old at least, and 151 women who died younger.

The results show that women who had a child after age 33 had twice as likely to live to age 95 or more than those who had their last child before age 29. The association between maternal age and longevity is, however, attenuated if women have 3 or more children. On the other hand, the positive association between maternal age and longevity remains significant even after adjusting for the family longevity factor.

“If a woman has the natural ability to have a child later, this means that her reproductive system is slowly aging, and therefore also the rest of her body. » says Thomas Perls, one of the authors of the study.

How many children to age more slowly?

A Finnish study published in Nature Communications provides new information on the relationship between reproduction and longevity (2). Conducted by the University of Helsinki on nearly 15,000 women followed since 1975, it shows that it is not only the age of the last pregnancy that counts but also the total number of children.

Women who had two to three childrenwith pregnancies occurring approximately between ages 24 and 38, have the most favorable aging profiles and the longest life expectancies.

Conversely, having more than four children is associated with shorter life expectancy and accelerated biological aging. According to biologist Mikaela Hukkanen, who led the study, this is explained by a fundamental energy trade-off: “When a large amount of energy is devoted to reproduction, it is taken away from the body’s maintenance and repair mechanisms, which could reduce lifespan. »

Another unexpected result: childless women also age faster than average, probably due to underlying hormonal, behavioral or health factors that could not be fully isolated in the analyses.

However, these data apply at the level of a population, not an individual. They do not demonstrate a cause and effect relationship, and do not constitute a recommendation on the number of children to have or the ideal age to conceive. “A woman should not consider changing her plans or wishes regarding children based on these findings”recalls Dr Ollikainen in a press release (3). Family sizes have decreased and age at first birth has increased since the period covered by the study.

Note that in the American study on longevity, the association between late maternal age and longevity also attenuates when women have three or more children — a result consistent with the Finnish data.

French and European women are having children later and later

The age at motherhood has increased continuously since 1980, according to INSEE (4). In France, the average age at first pregnancy was 29.1 years in 2023, or 5.1 years later than in 1974. This development reflects a European trend: the average age at first child was 29.8 years in 2023 in the European Union, ranging from 26.9 years in Bulgaria to 31.8 years in Italy.

Epigenetics: how pregnancies influence aging

What sets the Finnish study apart from previous work is the biological measurement of aging. The researchers used epigenetic clocks, molecular markers extracted from blood samples, to assess the real biological age of the participants, independently of their calendar age.

The results reveal that women who have had many or no children are biologically older than their actual age. “A person who is biologically older than their calendar age has a higher risk of death. Our results show that lifestyle choices leave a lasting biological imprint, measurable well before old age”underlines Dr. Miina Ollikainen, head of the study.

These epigenetic clocks make it possible to detect changes linked to aging years, even decades, before they result in diseases.

Genetics: common variants between fertility and longevity

The key to longevity is partly genetic. Studies on twins have shown that 20% of longevity is due to genetic factors and 80% to environmental and behavioral factors. Thus, by adopting your eating habits and changing certain behaviors (smoking, alcohol consumption, sedentary lifestyle, etc.), you can improve your life expectancy.

Read: Dietary polyphenols associated with longevity

Likewise, studies have shown that genetic variations influence lifespan. Thus, the possibility of discovering genetic variants linked to longevity is greater in centenarians than in nonagenarians.

It would seem that the genetic variants which allow a woman to naturally have a child late are the same as those which allow a slowdown in aging and influence the predisposition to age-related diseases. In other words, prolonged fertility could be a biological marker of slowed overall aging and not its direct cause.

In summary
Two to three children, pregnancies between the ages of 24 and 38, and if possible a last pregnancy after the age of 33: this is the reproductive profile associated, at the population level, with the best aging trajectories. A picture that reflects a favorable biology, partly genetic, and partly shaped by lifestyle habits.

Read also: Why the Mediterranean diet allows you to live longer in good health