A study has found that women with no childbirth experience may age biologically faster, similar to women who have given birth to many children.

In a 50-year follow-up of 14,836 pairs of twin sisters in Finland, women who had no children, women who had many children, and women who had their first child at a very early age showed a relatively faster pace of biological aging.

By contrast, women who on average had about two children, with their first birth at ages 24–25 and last birth at ages 29–30, showed the slowest rate of aging and tended to have a longer lifespan.

The large-scale twin study conducted by researchers from the University of Helsinki and the Minerva Foundation in Finland was published on the 8th (local time) in the international journal Nature Communications.

The researchers analyzed blood samples from 1,054 participants and applied several types of epigenetic clocks to assess biological age.

■ Accelerated aging also observed in nulliparous women
The most notable finding in this study was observed among women with no childbirth experience (nulliparous women). Contrary to expectations, their biological aging indicators tended to progress faster than their chronological age.

Previous research has mainly focused on results indicating that “having many births accelerates aging,” so the aging rate of nulliparous women has received relatively less attention.

The researchers cautiously suggested that this could be related to findings that pregnancy and breastfeeding are associated with reduced risks of certain hormone-related diseases, and that the absence of social support through children or health and lifestyle factors may have influenced both fertility and aging.



■ The same applies to women with many births
Not only among women with no childbirth experience, but also among women who had four or more children over their lifetimes, accelerated biological aging and increased mortality risk were observed together.

The researchers explained this as an “issue of energy allocation.”
According to the life-history theory of evolutionary biology, organisms, including humans, must allocate limited time and energy between reproduction (pregnancy, childbirth, breastfeeding) and bodily maintenance and repair. The more energy invested in childbirth, the fewer resources may remain in the long term for physical recovery and managing aging.

The researchers pointed out, “Pregnancy, childbirth, and breastfeeding impose a particularly heavy physiological burden on young mothers, and women who give birth early may be more vulnerable to the physical, emotional, and economic stresses associated with childrearing, with a higher likelihood of cumulative stress and allostatic load (wear and tear or damage to the body caused by stress).”

■ Women with very early first births also age faster
Women who had their first child at a very early age also tended to show a faster rate of aging.
The researchers interpreted this from an evolutionary perspective, suggesting that early reproduction can shorten the interval between generations and increase overall reproductive success within a lineage, but that the price for this may be accelerated aging later in life.

However, they added that this may be a direct effect of early childbirth itself, but it could also be due to other lifestyle or health-related factors that were not fully controlled for in this analysis.

■ Common traits of the slowest-aging women
Women who showed the slowest pace of biological aging and tended to have the longest average lifespan shared the following characteristics:

△ Number of births: average 2–2.4 children
△ Age at first birth: average 24.4 years
△ Age at last birth: average 29.8 years


The researchers explained that this was “not so much a special choice as the most common, average life course under the social and economic conditions of the time.”

Life-history theory often holds that choices that are “neither too early nor too late, and neither too many nor too few” tend to lead to the most stable outcomes. The fact that the reproductive patterns of the women with the longest healthy lifespans in this study were close to this “middle value” aligns well with the theory’s predictions.

They added that, beyond biological factors, socioeconomic and cultural conditions—such as the financial resources parents can afford, housing conditions and family structure, access to healthcare, and the burdens associated with raising children—likely acted to naturally constrain average timing and number of births.

■ Researchers caution: “Do not apply this to individual choices”
Lead researcher Dr. Miina Ollikainen stressed, “This study only shows statistical associations at the population level and in no way means that a woman must have a certain number of children to be healthy,” adding, “Individual women therefore should not attempt to change their reproductive plans or desires based on these findings.”

The researchers stated that the relationship between reproductive history, biological aging, and lifespan can vary depending on historical and cultural context, socioeconomic conditions, and individual health status, and thus has limitations in terms of generalization.

Related research paper link: https://dx.doi.org/10.1038/s41467-025-67798-y

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