Fathers who smoke are more likely to have children with asthma even if they quit the habit before their baby is conceived, according to new research.
The study authors found that a child's risk of developing asthma was greater if their father smoked before he was 15 years of age, and that risk increased with the number of years he had been lighting up.
The research, which was presented this week at the Annual Scientific Meeting of the Thoracic Society of Australia and New Zealand on the Gold Coast, adds to mounting evidence which links a father's exposures before conception to the health of a baby.
It is the first study time the link between a father's smoking habits before conception and a child's asthma has been analysed.
"This study is important as it is the first study looking at how a father's smoking habit pre-conception can affect the respiratory health of his children," Dr Jennifer Koplin, from the Murdoch Children's Institute, said when presenting the findings.
"Given these results, we can presume that exposure to any type of air pollution, from occupational exposures to chemical exposures, could also have an effect."
Australia's School of Population and Global Health, University of Melbourne, and the Murdoch Children's Institute, Melbourne, were involved in the research.
The study authors looked at 13,000 parents (both men and women) and 24,000 children.
They gathered information about the number of years mothers and fathers had smoked prior to a conception, the incidence of asthma in their children, and whether the parents had quit before the baby was conceived.
The results showed that non-allergic asthma (without hayfever) was significantly more common in children with a father who smoked prior to conception. This risk of asthma increased if a father smoked before the age of 15 and continued to increase the longer the duration of smoking.
The researchers found no link between the mother's smoking prior to conception and a child's asthma.
Dr Koplin said the findings were significant as they demonstrated the importance of raising awareness of the issue among young men.
"It is important for policymakers to focus on interventions targeting young men and warning them of the dangers of smoking and other exposures to their unborn children in the future," she said.
If men are thinking about becoming dads with their partner, they are advised that it's never too late to quit smoking. Smoking has been shown to affect sperm quality, which can make conceiving more difficult - and it's then safer for children to live in a smoke-free home.