Science backs up what parents know – fluctuating stress levels during pregnancy can lead to distressed babies

Today is Day 4 of the Jean Hailes Women’s Health Week 2022, an initiative dedicated to all women across Australia to make good health a priority.

There’s a word for when someone experiences big fluctuations in stress from one moment to the next – ‘lability’ – and researchers from Northwestern University in Illinois in the US, have uncovered links between increased levels of lability during pregnancy and unhappy babies.

Of course people have been aware of the links between stress levels and emotions of the parent and infant behaviour and temperament for some time. However, this is the first study to monitor women’s real-time levels of stress while pregnant, allowing for a more focussed look at how stress changes throughout the day rather than just using an average over the span of the pregnancy.

“Variability is inherent in our daily lives, so this lability is capturing an important aspect of stress and offers insight into how to measure it,” says research assistant professor Leigha MacNeill, lead study author from Northwestern.

“This is of particular importance as we work to closely capture the maternal-foetal environment as it relates to how babies develop.”

Over 14-week period pregnant women recorded their stress levels up to four times a day via questions sent to their phones. This established a baseline level of stress, enabling researchers to ascertain what was a typical level of stress across the 14 weeks, and also to detect fluctuations from one point to the next.

When their infants were three months old, mothers were sent a questionnaire regarding their child’s temperament, which resulted in an overall “negative affect score” for each infant. These included questions rating the child’s sadness, distress and fearfulness – measured by behavioural indications like clinginess when being introduced to an unfamiliar adult. 

Pregnant women who experienced high lability tended to have infants with more fear, sadness and distress.

“There may be something about that gestational experience, when a mother moves between extremes, that shapes the child’s disposition toward negative emotions,” MacNeill says. “That kind of stress pattern could reflect instability in daily life experiences, unpredictable external stressors or instability in how a mother perceives her lived experiences, which may have important implications for children’s emotional development.”

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Read More: Epigenetics and pregnancy stress: should we be scared?

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Importantly, some of the participants completed their assessments before the onset of the pandemic, so the research was also able to discount the effects of the pandemic on the study. “We found that mothers’ stress patterns were unrelated to the timing of the pandemic,” said MacNeill. “Mothers reported similar levels of stress regardless of whether their stress measurements occurred before or during the pandemic.”

There is a lot more to be done in this space. The researchers hope to expand their studies to follow the negative affect levels over the first year of the infants’ lives and continue trying to understand exactly how fluctuating stress impacts a developing foetus in this way. There is also a need to expand the sample to include more diversity.

Ultimately, this research could help develop better support systems and policies for families, with stress management becoming an important part of prenatal support visits.