New research has found a link between behavioural problems in children and smoking by their mothers during pregnancy.
The study - "Growing up in Ireland: National longitudinal study of children" - found children whose mothers smoked during pregnancy have a higher risk of behaviour problems at age nine.
The research also found that children whose mothers were heavy smokers were 78% more likely to have behavioural problems than those of non-smokers.
Children of occasional smokers were 32% more likely to display these problems.
The study also found that the proportion of mothers who smoke during pregnancy has fallen from 28% in the late 1990s to 17.6% now.