Your child has a 50 per cent heightened risk of asthma if you eat nuts or peanut butter pregnant and you have a strong family history of food allergies or allergic asthma.
Researchers made the connection when they tracked more than 4,000 pregnant women, 1,327 of whom had a history of allergy or asthma. Only nuts and related foods had a direct link to asthma in the child, while other foods associated with allergies - such as eggs and milk - didn't have the same effect.
A child whose mother rarely ate nuts wasn't affected; only those women who ate nuts every day increased a child's chances of developing asthma by 47 per cent.
In a separate study, children were found to more likely develop allergies and asthma if their mothers were stressed during pregnancy. Researchers found that stress may later the immune system of the foetus and could predispose the child to allergies in later life.
A mother's exposure to dust mites and other allergens while pregnant could also increase her child's chances of developing asthma.
And women who regularly use a mobile phone while they are pregnant could also be causing behavioural problems in their child. In a study involving more than 13,000 pregnant women, researchers have found that those who are frequent users of the phones increase the likelihood of their child developing problems such as hyperactivity, especially if the child also uses a mobile phone before the age of seven.
(Sources: Nut study: American Journal of Respiratory and Critical Care Medicine, 2008; 178: 124-31; stress study: proceedings of the American Thoracic Society, Toronto; mobile phone study: Epidemiology, 2008; 19: 523-9).