Researchers at the University of Helsinki and the Minerva Foundation Institute for Medical Research report that both the number of children a woman has and the timing of her pregnancies are associated with health in adulthood and overall life expectancy. Their findings suggest that reproductive history is reflected not only in later-life outcomes such as longevity, but also in broader patterns of ageing across the life course.
The analysis is based on a long-running twin cohort study in which participants were first invited to complete a comprehensive questionnaire in 1975. Since then, their lives have been followed at regular intervals for several decades. This extensive follow-up has allowed researchers to link early and midlife reproductive patterns with long-term health trajectories, making it possible to examine ageing and mortality outcomes in considerable detail.
Drawing on data from nearly 15,000 participants, the researchers found that women with two or three children tended, on average, to live the longest. The timing of pregnancies also appeared to be important. Women whose pregnancies occurred roughly between the ages of 24 and 38 showed more favourable ageing profiles and greater longevity than those whose pregnancies fell outside this range. These results point to a complex relationship between reproduction and ageing rather than a simple linear effect.
In contrast, women with an above-average number of children—defined in this study as more than four—were found to have shorter lifespans and signs of accelerated biological ageing. According to the researchers, this pattern is consistent with life history theory in evolutionary biology, which emphasises trade-offs in how organisms allocate limited resources. “From an evolutionary biology perspective, organisms have finite resources such as time and energy,” explains doctoral researcher Mikaela Hukkanen. “When a large share of these resources is invested in reproduction, fewer remain available for bodily maintenance and repair, which may ultimately reduce lifespan.”
One unexpected finding was that childless women also showed faster ageing than women with a small number of children. The authors caution that this association may be influenced by other lifestyle, social, or health-related factors that could not be fully controlled for in the analyses. They also stress that the results apply only at the population level. The study does not establish cause-and-effect relationships and should not be interpreted as guidance for individual reproductive decisions, particularly given that family size and age at first birth have changed substantially since the period covered by the data. “An individual woman should not consider changing her own plans or wishes regarding children based on these findings,” says study lead Dr Miina Ollikainen.
A novel aspect of the research was the inclusion of biological measures of ageing alongside mortality data. Epigenetic clocks were calculated from blood samples provided by more than one thousand participants, allowing researchers to estimate biological ageing by measuring molecular changes linked to the gradual deterioration of cells and tissues. These measures supported the mortality findings: women with either many children or no children at all were biologically older than their chronological age. “People who are biologically older than their calendar age face a higher risk of death,” Ollikainen notes. “Our results show that life history choices leave lasting biological imprints that can be detected long before old age.”
More information: Mikaela Hukkanen et al, Epigenetic aging and lifespan reflect reproductive history in the Finnish Twin Cohort, Nature Communications. DOI: 10.1038/s41467-025-67798-y
Journal information: Nature Communications Provided by University of Helsinki
