Pregnant women who suffer from stress are more likely to have a child with asthma, according to research from Children of the 90s study.
Researchers working with about 6,000 families in Bristol found anxious mums-to-be were 60% more likely to have a baby who would develop the illness.
The findings show 16% of asthmatic children had mothers who reported high anxiety while pregnant.
Mothers-to-be who were less stressed had a lower incidence rate.
Professor John Henderson, from the Children of the 90s team, said: "Perhaps the natural response to stress which produces a variety of hormones in the body may have an influence on the developing infant and their developing immune system that manifests itself later on."
The Children of the 90s study - carried out by the University of Bristol - has been following 14,000 children.
They are regularly tested and monitored to see how different lifestyles affect growth, intelligence and health.
The aim is to identify ways to optimise the health and development of children.
Key findings to come out of the project include left-handed children do less well in tests than their right-handed peers and women who eat oily fish while pregnant have children with better visual development.
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