Women who smoke while pregnant may harm their babies by chemically altering the DNA of the developing fetus, a major study including more than 6,000 women and children found on Thursday.
The new results reveal that smoking during pregnancy leaves a lasting mark on the genome that persists into childhood, and identifies the sites and genes in the genome that are especially susceptible to these effects, Reuters reported.
Doctors have long warned women to avoid cigarettes while pregnant because smoking can lead to stillbirth, or babies born with cleft palate, lung disease, or neurobehavioral problems.
Experts have not known much about 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 sustained smokers, 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. Many signals tied into developmental pathways, and changes were seen in genes relating to lung and nervous system development, smoking-related cancers, and birth defects such as cleft lip and cleft palate, the study said.
The DNA changes were documented in samples of umbilical cord blood drawn after birth. Such changes were less apparent in mothers who smoked less frequently during pregnancy.
A separate analysis found that some DNA modifications remained apparent in a group of hundreds of older children – those with an average age of six – whose mothers had smoked while pregnant.
