EVANSTON, Ill. — Pregnant women who experience wide fluctuations in stress give birth to children who can suffer from fear, sadness, and distress, a new study reveals. Researchers at Northwestern University say their work shows how these fluctuations, also known as lability, affect children’s development before they are even born.

Previous studies have shown how stress can affect unborn children, but this is the first to examine the effect on the ebb and flow of feeling stress at different times.

“Research often examines stress as a static, unchanging construct—one that is either high or low, present or absent—but most of us have a lot of ebbs and flows in our stress depending on what is going on around us,” says lead study author Leigha MacNeill, a research assistant professor of medical social sciences at Northwestern University Feinberg School of Medicine, in a media release.

“That variability is inherent in our daily lives, so this lability is capturing an important aspect of stress and offers insight into how to measure stress going forward. This is of particular importance as we work to closely capture the maternal-fetal environment as it relates to how babies develop over time.”

For example, Dr. MacNeill explained, one mother who has consistent levels of stress over pregnancy and another mother who moves between very low and very high levels of stress during pregnancy may in the end have a similar average level of stress across that time, but that average may not best capture meaningful differences in what the fetus experiences.

“There may be something about that gestational experience, when a mother moves between extremes, that shapes the child’s disposition toward negative emotions,” MacNeill continues. “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.”

Can doctors help mothers-to-be avoid stress?

The study author also says that having a better understanding of the nature of stress during pregnancy may help to prevent its negative effects. It could lead to helping mothers remain consistently calm before or at the onset of pregnancy, especially when experiencing uncontrollable life events. Since most expecting parents receive some form of prenatal care, Dr. MacNeill says, doctors should incorporate stress measures and management into those visits.

Published in the journal Infancy, the researchers sent participants a series of questionnaires. Although they didn’t set out to test pandemic-related stress, they used COVID’s arrival as part of the study, with some participants completing questionnaires before the pandemic began, some before and during, and some completely during the pandemic.

“We asked about general stress—not pandemic-related stress,” MacNeill explains. “But we took advantage of the occurrence of the pandemic during the course of the study to see if we could detect its impact on mothers’ experiences.”

“We found that mothers’ stress patterns were unrelated to the timing of the pandemic. Mothers reported similar levels of stress regardless of whether their stress measurements occurred before or during the pandemic.”

The study authors measured pregnant individuals’ stress up to four times a day for 14 weeks using questions sent to the participants’ phones. They identified three types of stress: stress at the first assessment (baseline), average or typical levels of stress across the 14-week period, and the amount a person changed in their stress from one time to the next across the 14-week period (lability).

The authors measured infants’ negative emotions via a temperament questionnaire given to mothers when their infants were three months-old. Mothers answered questions about their child’s sadness, distress to limitations, and fearfulness — for example, how much they clung to their parent when encountering an unfamiliar adult.

This formed an overall negative affect average score.

‘Parents are the ones who can soothe their infants’

Since studying stress fluctuations during pregnancy is a relatively new idea, the authors say that more research is necessary before a clear understanding can emerge of how stress impacts developing fetuses.

“This is a really early index (three months), so we’d want to see how consistent their negative affect levels are in the first year of life,” MacNeill says. “Parents are the ones who can soothe their infants and be really responsive to their needs, and as infants grow, there are things parents can do to help the child navigate situations and learn to regulate and cope with their negative emotions.”

“This study illustrates that links between parent and child are based on genes as well as experiences, even before birth,” concludes Dr. Matthew Davis, chair of the department of pediatrics at Feinberg and the Ann & Robert H. Lurie Children’s Hospital of Chicago, who did not directly take part in the study.

“One of the most important approaches to having a less distressed child is to support expectant parents and minimize their stress during pregnancy. That can be accomplished through clinical care, social supports and policies that are family- and pregnancy-friendly.”

South West News Service writer Danny Halpin contributed to this report.

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