Children who experienced multiple negative events before birth, such as exposure to alcohol or pre-eclampsia, are at higher risk of experiencing poor mental health a decade later.

Joshua Roffman at Harvard Medical School in Boston and his colleagues asked the parents of almost 10,000 children aged 9 or 10 years whether the children had experienced a range of negative events before birth. They also used a standard child behaviour questionnaire to identify children with mental health issues, including anxiety and depression.

The negative events the researchers looked at included exposure to alcohol, tobacco or marijuana both before and after the pregnancy was known, pregnancy complications and birth complications. They also looked at unplanned pregnancies. These have all previously been identified as individual mental health risks to children, but the team found that they have a compounding effect – children that had experienced the most events were at highest risk.

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“The risk increased relatively steeply as the number of exposures went up, so while children who had no such exposures only had about a 7 per cent risk of clinically significant symptoms at that age, those with four or more exposures had a 29 per cent risk,” says Roffman.

This could help identify families and children who may need more support, says Helen Dodd at the University of Reading, UK. “Some of it is about supporting women who are pregnant to prevent big exposures and some of it is also about using these exposures as ways of working out who might need the most support during those early years.”

The researchers used data collected through interviews and surveys to control for early childhood trauma and environmental variables including post-birth parental conflict and neighbourhood safety.

They also studied siblings and found that within families, children who had a larger number of prenatal negative events had worse mental health than their siblings who had fewer, suggesting that these events were a determining factor.

“I think the results underscore the importance of the prenatal environment and in particular the early prenatal environment to subsequent risk,” says Roffman. “It will be important to follow these kids as they age into the time period where risk of newly emergent psychiatric disorders is higher in later adolescence.”

Journal reference: PLoS One, DOI: 10.1371/journal.pone.0250235