0620 GMT January 18, 2020
While prenatal smoke exposure has long been linked to an increased risk of childhood asthma, the current study offers fresh evidence that it's not just a pregnant mother's smoking that can cause harm, Reuters reported.
Researchers followed 756 babies for six years. Almost one in four were exposed to tobacco by fathers who smoked while the child was developing in the womb; only three mothers smoked.
Overall, 31 percent of kids with fathers who smoked during pregnancy developed asthma by age six, compared with 23 percent of kids without fathers who smoked, the study found.
Asthma was also more common among kids whose fathers were heavier smokers, senior study author Dr. Kuender Yang of the National Defense Medical Center in Taipei said by email.
"Children with prenatal paternal tobacco smoke exposure corresponding to more than 20 cigarettes per day had a significantly higher risk of developing asthma than those with less than 20 cigarettes per day and those without prenatal paternal tobacco smoke exposure," Yang said.
About 35 percent of the kids with fathers who were heavier smokers developed asthma, compared with 25 percent of children with fathers who were lighter smokers and 23 percent of kids with fathers who didn't smoke at all during pregnancy.
Smoking by fathers during pregnancy was also associated with changes in methylation — a chemical code along the DNA strand that influences gene activity — on portions of genes involved in immune system function and the development of asthma.
Researchers extracted infants' DNA from cord blood immediately after birth and examined methylation along the DNA strand. The more fathers smoked during pregnancy, the more methylation increased on stretches of three specific genes that play a role in immune function.