Smoking in expectant mothers causes complications such as preterm delivery, low birth weight and health issues in their children. But can a father's smoking habit during teenage years affect the health of a child? A new study has found that boys who smoke in their early teens risk passing damaged genes to their future kids.

Findings of a recent study published in the journal Clinical Epigenetics suggest that the effect of smoking can last for generations. Moreover, it hints that smoking in the teenage years causes DNA changes in the sperm which then results in alterations in the DNA of their future babies, elevating the risk of developing asthma and obesity and reducing lung function.

The research team evaluated the epigenetic profiles (the DNA changes) of 875 participants between the ages of 7 and 50 and the smoking habits of their fathers. The DNA changes associated with asthma, obesity and wheezing were seen to be more pronounced in those participants whose fathers started smoking before the age of 15.

"Changes in epigenetic markers were much more pronounced in children whose fathers started smoking during puberty than those whose fathers had started smoking at any time before conception," Negusse Kitaba, co-lead author of the study, said in a news release.

"Early puberty may represent a critical window of physiological changes in boys. This is when the stem cells are being established which will make sperm for the rest of their lives," Kitaba explained.

The researchers examined how fathers smoked before having children and compared them to participants who smoked themselves, as well as to mothers who smoked before becoming pregnant.

"Interestingly, we found that 16 of the 19 markers associated with fathers' teenage smoking had not previously been linked to maternal or personal smoking. This suggests these new methylation biomarkers may be unique to children whose fathers have been exposed to smoking in early puberty," Gerd Toril Mørkve Knudsen, another co-lead author of the study, said.

According to Julian Laubenthal, a co-author of the study, men should quit the habit of smoking well in advance of trying to conceive as a fertile sperm cell takes around three months to develop.

The study suggests that neglecting to address harmful exposures in young teenagers today may adversely affect the respiratory health of future generations.