New study links smoking among pregnant women with DNA alterations in their babies

A new study has linked smoking among pregnant women with DNA differences in their babies' DNA that mirrored alterations in adult smokers and suggested how smoking might contribute to certain birth defects.

Researchers analysed data on mothers and their newborn children to understand how smoking influenced DNA methylation, a chemical code along the DNA strand that controlled some DNA mechanics, and when genes got activated. Whether certain points along the DNA molecule were methylated or not could determine everything from eye colour to a person's predisposition to certain diseases.

Among women who 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 a collection of genes involved in 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, Reuters reported.

"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.

Experts had little knowledge of how these changes to DNA take root in the fetus, so they performed a meta-analysis of 13 prior, smaller studies, some of which had suggested links between smoking and chemical modifications to DNA, also known as methylation.

Among the mothers who smoked regularly researchers identified "6,073 places where the DNA was chemically modified differently" than in the newborns of non-smoking moms.

"About half of these locations could be tied to a specific gene," said the study, published in the American Journal of Human Genetics.

According to co-author Bonnie Joubert, an epidemiologist at the National Institute of Environmental Health Sciences (NIEHS), many signals tied into developmental pathways.