A study published recently in Environmental Health Perspectives concludes that no amount of exposure to secondhand smoke is safe for pregnant women. Led by researchers at Virginia Commonwealth University Massey Cancer Center, the study is the first to look at the link between secondhand smoke during pregnancy with epigenetic modifications to disease-related genes.
"What we recommend to mothers, in general, is that no level of smoke exposure is safe," said study lead author Bernard Fuemmeler, Ph.D., M.P.H., associate director for population science and interim co-leader of the Cancer Prevention and Control program at VCU Massey Cancer Center. "Even low levels of smoke from secondhand exposure affect epigenetic marks in disease-related pathways. That doesn't mean everyone who is exposed will have a child with some disease outcome, but it contributes to a heightened risk."
The team arrived at these conclusions after an extensive analysis of pregnant women enrolled in the Newborn Epigenetics Study (NEST) between 2005 and 2011. The women in the study had exposure to ranging levels of secondhand smoke (from essentially none to levels consistent with secondhand smoke), measured by the presence of the nicotine byproduct cotinine in their blood. Following the birth of the study participants’ children, the researchers analyzed the umbilical cord blood that is responsible for bringing blood to the fetus in utero. They then conducted an epigenome-wide association study to look for correlations between blood cotinine levels of the mothers during pregnancy and epigenetic patterns in the babies at birth.
The ideology behind this study stems from the epigenetic emphasis that many adult diseases develop due to environmental exposures that occur during early development. Epigenetic changes refer to changes to how genes are regulated rather than changes to the genetic code itself.
The team found that in women with higher levels of cotinine, the newborns were more likely to have epigenetic "marks" on genes that control the development of brain function, as well as genes related to diabetes and cancer. In a follow-up analysis, they found that cotinine levels are also correlated with the regulation of genes involved in inflammation and diabetes, as well as the regulation of cardiovascular and nervous system functions.
"It highlights the importance of clean air," said Fuemmeler. "It's important not only for our homes but also in the environment. Clean air policies limit smoke in public, and for pregnant women that may have long-term effects on offspring."