Cortisol in pregnancy can reshape baby brains

3 minute read

And the effects differ by sex of the fetus, a new study has found.

Maternal stress levels during pregnancy appear to influence the shape and connectivity of the baby’s amygdala, which plays a key role in emotional regulation.

Previous epidemiological studies have shown that babies exposed to stress in the womb are at higher risk of developmental mood conditions such as ADHD and depression.

Now a new study suggests variations in cortisol levels have different impacts on male and female babies – and its findings emphasise the importance of stress management during pregnancy for all women, an independent expert says.

“This effect is different between the sexes, and the biological mechanisms that underpin these observations are poorly understood,” the authors wrote in the study, published in eLife.

The researchers, led by the University of Edinburgh, measured cortisol concentrations in 3cm hair samples taken close to the scalp, postnatally, from 78 women.

This sampling approach has been previously established as an accurate measure for activity in the hypothalamic-pituitary-adrenal axis (HPA) in the previous three months, the authors said.

Unlike saliva or blood samples, the reading isn’t influenced by short-term responses to acute stress.

The median hair cortisol concentration was 5.6 pg/mg.

By linking the cortisol levels to MRI scans of the newborns taken around 42 weeks of age, they found exposure to higher cortisol levels in the womb affected babies differently based on their sex: males had alterations in the fine structure of their amygdala, while females displayed changes in the way that brain region connected to other neural networks.

“To our knowledge, this is the first study to investigate a physiological measure of chronic maternal HPA activity with quantitative biomarkers of brain development,” the authors said.

Limitations include an insufficient sample size to detect both sex and birth gestation interactions, and long-term studies including socio-emotional development measures are now needed to understand the functional consequences of their results, they said.

However, “The data lend further support to strategies designed to optimise pre-and-early pregnancy health for optimising fetal neurodevelopment.

“Given the fundamental role of the amygdala in the emergence of emotion regulation, these findings offer new insights into mechanisms linking maternal health with neuropsychiatric outcomes of children.”

GP Dr Nicole Hall said that while the cohort is small and more research is needed, the results are interesting.

“We are continuing to gather data on the fact maternal stress can have significant implications on a developing fetus which has implications for years to come, and that supporting pregnant women during their pregnancy emotionally and mentally is of the utmost importance,” said Dr Hall, who is Deputy Chair of the RACGP Antenatal/Postnatal Care Specific Interests Network.

“This [study] is significant as it emphasises a difference between sexes in fundamental brain formation and its subsequent effect on behaviour and emotion. We know in practice that there is a difference in emotional regulation between boys and girls, this helps to provide a scientific reason for this.”

The findings are particularly relevant given the large number of reports of mental health concerns during the COVID-19 pandemic, Dr Hall added.

It was important that women have access to well-delivered information about the impact of stress on their pregnancies, so that misinformation does not exacerbate stress, she said.

“Women need to … be aware to seek advice from their GP as there is much that can be done to help support women through the antenatal period.

“General practitioners are well placed to provide this and help women engage with other support services as needed. Further, this information may prove useful in the future for how we deal with emotional and behavioural problems shown by children.”

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