You might get more passed down from your grandparents than just the color of their eyes or the shape of their nose. A recent study presented at the European Respiratory Society’s International Congress has found that grandmothers who smoked during their pregnancies passed along an increased risk of asthma to their grandchildren — even if the mother didn’t smoke.

With asthma and allergy rates rising in recent years, scientists have attempted to understand the underlying causes. Some believe it’s due to an increased use of antibiotics and acetaminophen; others have found that obesity or vitamin D deficiency may play a role. But the new study focuses on how the smoking habits of mothers and grandmothers increases the risk of asthma in later generations.

In the study, the researchers examined 44,853 grandmothers between the years of 1982 and 1986, using information from the Swedish Registry. They were able to see the grandmothers’ smoking habits during pregnancy, and compare it to the use of asthma medication in 66,271 grandchildren. The researchers found that if grandmothers had smoked during their pregnancy, the risk of asthma among grandchildren (even if their mothers didn’t smoke) was increased by 10 to 22 percent.

“We found that smoking in previous generations can influence the risk of asthma in subsequent generations,” Dr. Caroline Lodge, an author of the study and Research Fellow at the University of Melbourne, Australia, said in the press release. “This may also be important in the transmission of other exposures and diseases.”

If past research is any indication, the notion of smokers passing down asthma from generation to generation isn’t surprising. One 2014 study found that pregnant mothers who were exposed to air pollution — which is damaging to lungs and health like cigarette smoke — increased their child’s risk of asthma. And a 2011 study found that children who were exposed to cigarette smoke before birth were 3.6 times more likely to develop asthma than children who weren’t.

“For us to understand more about the asthma epidemic, we require a greater understanding of how harmful exposures over your lifetime may influence the disease risks of generations to come,” Lodge continued in the press release. “Additionally, researchers in this area need to be aware, when interpreting the asthma risk from current exposures and genetic predisposition, that individuals may carry an inherited, non-genetic, risk from exposures in previous generations. This knowledge will help to clarify the findings concerning current risk factors in asthma research.”

Their study, however, only focused on grandmothers and their daughter’s children; a new study would need to examine the same asthma-smoking link in smokers’ sons and grandchildren.

“The next stage for the research team is to investigate the potential inheritance of asthma risk through the male line, by assessing the risk of asthma in grandchildren whose grandmothers smoked whilst pregnant with their fathers,” Professor Bertil Forsberg, another author of the study, said in the press release. “The findings also encourage research into inherited disease risks for other environmental exposures.”

Source: Lodge C, Forsberg B. European Respiratory Society’s International Congress. 2015.