Racking up sleepless nights while caring for a newborn may make new mothers feel old beyond their years — but research suggests that pregnancy may in fact accelerate biological ageing in women.
A study of young people in the Philippines found that women who reported being pregnant showed more signs of biological ageing than those who had not, with women who had been pregnant more times appearing older than those who had had fewer pregnancies.
The research found that each pregnancy appeared to age the women by 2.4 or 2.8 months, according to two of the measures of biological age used.
Parenthood has long been a burden shouldered by women and the research suggests this to be true biologically speaking as well. Signs of accelerated biological ageing were not seen in the 910 men taking part in the study, regardless of how many children they had. This led researchers to suggest that their findings were linked to pregnancy or breastfeeding, not parenthood itself.
The scientists from Columbia University’s Mailman School of Public Health used blood samples from the participants to assess the subtle changes in their cells associated with ageing.
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Factors such as genetics, diet and stress can all affect the “biological age” of different organs and cells, which may be different from a person’s chronological age — and the biological age of these can be calculated using algorithms, called “epigenetic clocks”. When an organ is classified as substantially older than a person’s true age, it usually means that it has accumulated damage at a faster rate — often increasing the risk of disease and premature death.
“Our findings suggest that pregnancy speeds up biological ageing and that these effects are apparent in young, high-fertility women,” said Calen Ryan, the lead author of the study and an associate research scientist in the Columbia Aging Center. “Our results are also the first to follow the same women through time, linking changes in each woman’s pregnancy number to changes in her biological age.”
“Epigenetic clocks have revolutionised how we study biological ageing across the life course and opened up new opportunities to study how and when long-term health costs of reproduction and other life events take hold,” Ryan added.
Those taking part in the study gave a blood sample and completed a survey in 2005 and a second time between 2009 and 2014 to measure the number of children they had and their biological age.
Published in the Proceedings of the National Academy of Sciences, the study’s 1,735 participants were aged between 20 and 22 at the first measurement, with many of the women reporting that they had had children in the initial measurement. While the research team took into account lifestyle factors such as smoking and socioeconomic status, they urged caution in interpreting the findings. As many of the women were in late adolescence at their first pregnancy, this could mean pregnancies at this young age may take more of a biological toll.
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“Many of the reported pregnancies in our baseline measure occurred during late adolescence when women are still growing,” Ryan said. “We expect this kind of pregnancy to be particularly challenging for a growing mother, especially if her access to healthcare, resources or other forms of support is limited.”
The team also added that the findings may reflect ageing in the Philippines specifically and not in other nations. Ryan said: “Ultimately, I think our findings highlight the potential long-term impacts of pregnancy on women’s health and the importance of taking care of new parents, especially young mothers.”
It is understood by scientists that pregnancy and breastfeeding use an extraordinary amount of energy and can have an impact on many systems, such as immune function, metabolism and blood pressure. However, some of the same researchers had previously found in 2020 that, in a cohort of American women, pregnancy accelerated ageing later in life — after a woman has experienced menopause.
“We think there’s something going on, some sort of trade-off, between ageing and reproduction,” Talia Shirazi, one of the researchers, told ScienceDaily at the time. “This makes sense from an evolutionary biology point of view because if you’re spending energy in pregnancy and breastfeeding, you probably don’t have as much energy to allocate towards things like physiological maintenance and defence.”
