Mothers who smoke while pregnant could be putting their child at increased risk of behavioural problems during the first three years of their lives, research has claimed.
Scientists at the University of York say such children are more likely to suffer from attention deficit disorder, hyperactivity and other problems than children whose mothers did not smoke while pregnant.
The research comes shortly after a separate investigation at Cardiff University found evidence of a link between smoking when pregnant and an increased risk of psychosis in children.
The "association study" - a label meaning no definitive conclusions can be drawn from the investigation - has been welcomed by the Centre for Maternal and Child Enquiries, who described it as "interesting".
Group chair, Professor Jimmy Walker, said: "We know that smoking affects foetal growth and placental function, and it could well affect the developing brain."