Smoking during pregnancy leads to an increased risk of children developing mental health problems, according to a new report. The NHS already warns mothers-to-be that smoking makes a miscarriage, premature birth or low birth weight more likely.

Research led by Dr Stanley Zammit of Cardiff University's School of Medicine has now discovered that maternal tobacco use can also have a long-term impact. His team's study, which is published in the British Journal of Psychiatry, established a link between smoking during pregnancy and psychotic symptoms in teenagers.

Researchers also discovered that the number of cigarettes smoked during pregnancy influenced the likelihood of children experiencing psychotic symptoms. Teenagers whose mothers smoked heavily during pregnancy were found to be at greatest risk. The experts were unable to find a reason for the link and suggested that further studies should be undertaken to look at how exposure to tobacco in the womb affects the brain.