The children of women who smoke during pregnancy may be more likely to have conduct problems, a new study suggests.

According to UK researchers, conduct problems among children appear to be on the rise worldwide. As smoking during pregnancy has already been linked to psychological problems in children, they decided to investigate the possible link between the habit and conduct further.

They assessed the link in children who were raised by their birth mothers and non-birth mothers, i.e. children who were adopted.

The researchers from the University of Leicester in the UK analysed three studies, which included children who had been adopted and who had been raised by their genetic mothers. The amount of cigarettes smoked during pregnancy was also measured.

The study found a significant link between maternal smoking during pregnancy and conduct problems in the children born to them. The link remained even if the woman smoked during pregnancy, but then gave the child up for adoption.

"Our findings suggest an association between pregnancy smoking and child conduct problems that is unlikely to be fully explained by postnatal environmental factors, i.e. parenting practices," the researchers said.

The reason for this link ‘is not known, but may include genetic factors and other prenatal environmental hazards, including smoking itself', they added.

Details of these findings are published in the journal, JAMA Psychiatry.

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