Smoking While Pregnant Could Alter Baby's DNA

Women who smoke while they’re pregnant may actually be impairing the DNA of their future babies. A new study comparing nearly 900 infants identified 10 genes with newly established links to maternal smoking. 

A plethora of problems could result from smoking during pregnancy, according to the Centers for Disease Control and Prevention: premature birth, low birth weight, Sudden Infant Death Syndrome, and a cleft lip or cleft palate, for example. Certain health and behavioral problems could follow these children into adulthood. 

We have a limited understanding of the biological mechanisms underlying these effects,Science explains, though one possibility is epigenetic changes. That’s when environmental factors, like smoking or diet, chemically modify DNA by turning certain genes on or off. DNA methylation is one such epigenetic modification. This occurs when a methyl group -- a chemical tag consisting of one carbon bonded to three hydrogen atoms -- is added to certain DNA bases. 

A team led by Christina Markunas from the National Institute of Environmental Health Sciences (NIEHS) conducted an epigenome-wide association study to investigate the alterations in DNA methylation in infants who were exposed “in utero” to tobacco smoke by their mothers. A genome-wide association study is a tool used by researchers to compare DNA from people with a disease (or a set of circumstances of interest) to similar people without it, in order to see what shows up more frequently with the disease being studied.  

The team used data from the Norway Facial Clefts Study, where families of hundreds of newborns with cleft lips or cleft palates participated. The researchers assessed DNA methylation in blood samples from 889 infants shortly after delivery. Of their mothers, 287 reported smoking during the first trimester -- making this the largest study on maternal smoking of its kind.

The DNA of babies born to mothers who smoked, they found, showed epigenetic changes that weren’t seen in the babies of nonsmokers. The team identified 110 gene regions with altered methylation in infants of smokers, and of those, 10 are newly confirmed and now implicated in nicotine dependence and placental and embryonic development. 

“If maternal smoking can alter the DNA methylation profile of newborns, other environmental exposures to chemicals, such as those found in the air, our homes and food, during pregnancy may also have epigenetic effects,” Markunas and study author Allen Wilcox also of NIEHS tell Science jointly. “We have only scratched the surface of how exposures during pregnancy might affect the baby.”

The work was published online in Environmental Health Perspectives last month.