Pregnant women now have another reason to quit smoking - a new analysis links it to differences in their babies' DNA that mirror alterations in adult smokers and suggest how smoking might contribute to certain birth defects.
Researchers analyzed data on mothers and their newborn children to see how smoking influences DNA methylation, a chemical code along the DNA strand that controls some DNA mechanics and when genes get activated. Whether certain points along the DNA molecule are methylated or not can determine everything from eye color to a person's predisposition to certain diseases.
When women smoked daily during pregnancy, researchers identified 6,073 places where their babies' DNA was methylated differently from the DNA of nonsmokers' infants.
Many of the differences were found on or near a collection of genes related to lung and nervous system development, smoking-related cancers and birth defects such as cleft lip and palate.
"We already knew that smoking during pregnancy, or after the child is born, is to be avoided at all costs," said senior study author Dr. Stephanie London, deputy chief of the epidemiology branch at the National Institute of Environmental and Health Sciences in Research Triangle Park, North Carolina.
"This study provides more evidence - signals you can see at birth that are similar to signals you can see in adult smokers," London added by email.
Researchers pooled results from 6,685 mothers and their newborns from studies performed around the world.
Most of the women said they didn't smoke, but about 13 percent of the women were daily smokers and another 25 percent admitted to occasional smoking during pregnancy.
To analyze methylation patterns in newborns' DNA, researchers collected samples mainly from blood in the umbilical cord after delivery. In addition to documenting differences between the infants of nonsmokers and regular smokers, the researchers looked at a smaller group of older children and found that at least some of the smoking-related methylation differences in the children of mothers who were smokers during pregnancy persisted.
While the study doesn't prove how maternal smoking may influence child development or disease, the findings suggest that DNA methylation differences might be involved in the appearance of certain birth defects or medical problems in babies born to mothers who smoke, the authors conclude in The American Journal of Human Genetics.
Follow NEWS.am Medicine on Facebook and Twitter