A new study finds a link between DNA changes in the sperm of male smokers and genetic changes in their newborn children. The research suggests that these changes may increase children’s risk of developing genetic diseases.

The findings indicate that men should stop smoking before they try to conceive, because a fertile sperm takes about three months to fully develop, according to researchers at the University of Bradford in England. “Anti-smoking campaigns are usually aimed at pregnant women, but couples planning their families—and public health policy-makers—need to know that the father must stop smoking before conception to avoid risking the health of the baby,” lead researcher Diana Anderson said in a news release.

She measured genetic changes in fathers’ blood and semen around the time of conception, as well as mothers’ blood and umbilical cord blood at the time of delivery, in 39 families. The families were asked about their lifestyle, as well as their occupational and environmental exposures, UPI reports.

“These transmitted genetic changes may raise the risk of developing cancer in childhood, particularly leukemia and other genetic diseases,” Anderson said. “We hope that this knowledge will urge men to cease smoking before trying to conceive.” She noted the study does not show a direct cause-and-effect relationship between a father’s smoking and any specific disease. She added, “It’s evident that that the lifestyle of men before they try to conceive can directly affect the genetic information of their children.”

The findings appear in the FASEB Journal.