Children who are exposed to tobacco smoke from their fathers while theyre in the womb may be more likely than those who are not to develop asthma by age 6, according to a study of chemical changes to DNA.

While prenatal smoke exposure has long been linked to an increased risk of childhood asthma, the current study offers fresh evidence that its not just a pregnant mothers smoking that can cause harm. Smoking by fathers during pregnancy was also associated with changes in DNA methylation on portions of genes involved in immune system function and the development of asthma. The findings are published in Frontiers in Genetics.