Children with grandmothers who smoked have an increased risk of asthma even when mothers did not smoke, according to new findings.

The new study, presented at ERS 2015, is the first to investigate the risk in a whole population and use evidence about smoking habits taken directly from grandmothers at the time they were pregnant.

The results found that if grandmothers had smoked while they were pregnant, there was an increased risk of asthma in grandchildren, even if their mothers had not smoked during pregnancy. The risk of asthma was increased by 10 to 22%.