Stress During Early Pregnancy Affects Offspring into Adulthood

Maternal stress hormone levels during early pregnancy can have a lasting effect on the offspring’s stress system. The results of a long-term study of wild Assamese macaques in Thailand suggest that maternal stress in the first half of pregnancy is particularly relevant. Increased stress hormones at a later stage during pregnancy or after birth did not have the same effects. The long-term study by the University of Göttingen and the German Primate Center – Leibniz Institute for Primate Research provides important insights into the influence of early life on the development of the stress system under natural environmental conditions.

Effects on the Stress Axis of Offspring

The research team investigated how maternal stress affects the stress hormone system of the offspring. The researchers found that exposure to maternal glucocorticoids during development can significantly affect the activation of the hypothalamic-pituitary-adrenal (HPA) axis, which plays a central role in stress management. The early phase of organ development in the first half of pregnancy proved to be a particularly critical time. “Our results show that the activity of the HPA axis of the offspring was stronger the more adversity the other had experienced during early pregnancy – for example, through food scarcity or social conflict,” says Simone Anzá, former doctoral student at the University of Göttingen and the German Primate Center and first author of the study.

In contrast to laboratory studies, the monkeys were observed in their natural habitat. Over a period of nine years, the researchers repeatedly collected fecal samples from pregnant females and measured the concentration of glucocorticoid metabolites in them to determine the animals’ exposure to environmental factors such as food scarcity, temperature fluctuations and social interactions. These values were compared with the stress hormone levels of the offspring at different ages. The effects on the offspring’s stress axis were evident from infancy through adolescence to adulthood at nine to ten years of age.

Previous analyses of the same study had already shown that early prenatal stress was also associated with altered growth, negative changes in the intestinal microbiome and impaired immune function, underlining the comprehensive influence of the environment in the early prenatal phase on various physiological systems. In contrast, maternal glucocorticoid levels in late pregnancy or during breastfeeding had no or different effects.

Reducing Long-Term Health Risks

“Our research suggests that the timing of maternal stress hormone exposure during and after pregnancy has a decisive influence on the consequences for the development and health of the offspring. Importantly, these effects do not require catastrophic events, but rather that even moderate changes in environmental conditions are sufficient,” says Oliver Schülke, a scientist at the University of Göttingen and the German Primate Center, and head of the study. Stress during early pregnancy can also have long-term effects on human health and increase the risk of stress-related illnesses and immune problems. According to the researchers, the results can help identify the timing and mechanisms on which preventive measures should focus in order to reduce long-term health risks.