Mothers who are stressed during pregnancy appear to be more likely to have children with allergies and asthma, new research suggests.

Experts at Harvard Medical School found that the cord blood of infants whose mothers were stressed during pregnancy contained higher levels of immunoglobulin E (IgE), a protein linked to allergies, even when exposed to relatively low levels of dust mite.

The researchers say that the mother's stress may magnify the effect of dust exposure on the child's immune system.

Dr Rosalind Wright, assistant professor of medicine at Brigham & Women's Hospital and Harvard Medical School, commented: 'Certain substances in the environment that cause allergies, such as dust mites, can increase a child's chance of developing asthma and the effects may begin before birth.

'This research adds to a growing body of evidence that links maternal stress such as that precipitated by financial problems or relationship issues, to changes in children's developing immune systems, even during pregnancy.'

The findings were presented at the American Thoracic Society's international conference in Toronto.