Why dads who smoke can cause unborn child to develop asthma later in life

Why dads who smoke can cause unborn child to develop asthma later in life

By Kristelle Bechayda

Children who are exposed to tobacco smoke from their fathers while they were still in the womb may be more likely to develop asthma by the age of six. This is according to a study recently published in Frontiers journals.

Prenatal exposure has long been linked to an increased risk in childhood asthma and the new study is offering fresh evidence that it isn’t just a pregnant mother’s smoking that can cause harm.

More than 30 percent increased risk

Following 756 babies for six years, the researchers noted that almost one in four were exposed to tobacco by fathers who smoked while the child was still developing in the womb. Meanwhile, only three mothers smoked.

The study found that 31 percent of the children whose fathers smoked during pregnancy developed asthma by the age of 6, compared to 23 percent of kids whose fathers didn’t smoke.

According to senior study author Dr. Kuender Yang of the National Defense Medical Center in Taipei, Asthma was also more common among children whose fathers were heavier smokers.

“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.

The study also showed 35 percent of the kids whose fathers were heavier smokers developed asthma, as compared to 25 percent of those with dads who were lighter smokers, and 23 percent of children whose fathers didn’t smoke at all during pregnancy.

What smoke exposure does to developing fetus

After the babies were born, the researchers immediately extracted their DNA from cord blood and examined methylation along the DNA strand. The more fathers smoked during pregnancy, the more methylation increased on the three genes that play a role in immune function.

The study found that children with the greatest methylation increases at birth had almost twice the risk of having asthma by the age of six compared to the others.

Despite the link between father’s smoking during pregnancy and childhood asthma, the former has no impact on the children’s sensitivity to allergens or total levels of IgE, which is an antibody associated with asthma.

Quit smoking before you have a baby

According to Dr. Avni Joshi, a researcher at the Mayo Clinic Children’s Center in Minnesota, the results suggests that the risk of asthma from tobacco exposure is different from allergic asthma, which is driven by allergies or allergic sensization through IgE antibody.

Although it isn’t clear yet how the changes seen in the DNA strand where methylation increase might cause asthma, Joshi noted that parents should quit smoking when they decide to have children.

“Smoking is bad at ANY point in time: before the baby is born and after the baby is born,” Joshi said. “Many parents defer quitting until the baby is born, but this study stresses that the prenatal exposure to tobacco creates changes to the unborn child’s immune system, hence it is best to quit as a family decides to have children, even before the conception happens.”

Story from Reuters.