According to researchers, smoking during pregnancy significantly increases the risk of having a child with behavioural problems. Writing in the Journal of Epidemiology and Community Health, UK and US researchers say the problems can be evident in children as young as three years old. They believe smoking in pregnancy may damage the developing structure of the baby's brain. The researchers from the universities of York, Hull and Illinois looked at more than 14,000 mother and child pairs. They found smoking in pregnancy may have direct effects on the foetal development of brain structure and functioning. One expert said, it was another strong reason for mothers to give up smoking.