A nine-year study of wild monkeys in Thailand has discovered a critical window in early pregnancy where maternal stress may permanently alter their offspring’s ability to cope with life’s challenges, which could impact human health and development.
Scientists tracking Assam macaques at Thailand’s Phu Khieo Wildlife Sanctuary found that exposure to elevated stress hormones during the first half of pregnancy was associated with lasting changes in offspring’s stress response systems that lasted into adulthood. The study, published in Proceedings of the Royal Society B, provides rare insights into how conditions early in life influence long-term health outcomes in nature.
What’s particularly striking about this finding is that these effects don’t require a major traumatic event—even modest environmental stressors, such as food shortages or social tension during early pregnancy, can trigger lasting physiological changes in offspring.
Unlike controlled laboratory studies, this study observed real-life challenges faced by animals in their natural habitats. For nearly a decade, researchers have repeatedly collected and analyzed stool samples from pregnant women to measure their exposure to various environmental stressors.
“Our results show that the more adversity the mother experiences early in pregnancy, such as food shortages or social conflict, the greater the HPA axis activity in the offspring,” explains Simone Anzá, lead author of the study and a former doctoral student. students at the University of Roots and the German Primate Center.
It turns out that the timing of stress exposure is critical. Research shows that elevated maternal stress hormones in late pregnancy or while breastfeeding do not have the same effects as early in pregnancy, when organs are first starting to develop.
Previous analyzes from the same study have demonstrated that early prenatal stress is associated with altered growth patterns and negative changes in gut microbiome composition, suggesting that these early effects can affect multiple body systems simultaneously.
Oliver Schülke, who led the study at the University of Göttingen and the German Primate Center, said: “Our results show that the timing of maternal exposure to stress hormones during and after pregnancy has an impact on the offspring. have a vital impact on development and health.
The team’s detailed analysis revealed that only about 2% of growth rings in pine and juniper shrubs showed stress-related changes. However, these changes are particularly concentrated in specific years consistent with known environmental events.
These findings could have important implications for human health because similar biological mechanisms are at work in primates. Understanding how and when maternal stress affects development can help medical professionals provide better preventive care during pregnancy.
Research suggests that paying special attention to the mother’s physical and mental health early in pregnancy may be particularly important for offspring health. “Our findings may help identify timing and mechanisms that preventive measures should address to reduce long-term health risks,” Schulke added.
The study used a unique approach to examine these effects in wild populations rather than in laboratory settings, providing a more complete understanding of how environmental stressors influence development under natural conditions. This real-world context helps scientists better understand the subtle but important ways in which early life experiences shape long-term health outcomes.
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