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Women Who Smoke While Pregnant Could Alter Their Children’s Genes

Researchers find link between maternal smoking and altered DNA methylation

The largest study of its kind has shown that smoking during pregnancy could cause epigenetic changes in the fetus, resulting in birth defects and health problems later in life.

Investigators at the National Institute of Environmental Health Sciences have found that newborn children of mothers who smoked while pregnant were more likely to have experienced certain changes to their DNA than were newborn children of non-smokers.

The research appears in the July 2014 issue of Environmental Health Perspectives.

Children exposed to tobacco smoke in utero have a higher risk of birth defects and are more likely to experience some medical problems than are the children of women who did not smoke while pregnant, the report says. This disparity between the children of smokers and the children of non-smokers continues into adulthood.

While scientists aren’t sure why smoking during pregnancy causes these problems, earlier studies have suggested that exposure to toxins in tobacco smoke could cause changes to the DNA of the developing fetus. Of the more than 7,000 chemicals in tobacco smoke, hundreds are harmful, and at least 69 are carcinogens.

In a study reported in 2011, researchers examined the possibility that exposure to tobacco smoke could cause changes in DNA methylation (the addition of a methyl tag to a gene). Alterations in DNA methylation can change how a gene functions and can increase the risk of developing certain diseases, including cancer. That study, which looked at DNA from the cheek cells of 173 children and their mothers, found that children whose mothers smoked while pregnant were twice as likely to experience DNA methylation of a gene involved in the immune response and many types of cancer than were the children of mothers who did not smoke during pregnancy.

In the new study, the researchers analyzed blood samples from 889 newborns, of which 287 had mothers who reported smoking in the first trimester of pregnancy. The investigators found a link between maternal smoking and altered methylation in 110 gene regions.

Some of the affected genes play a role in placental and embryonic development, in substance abuse, in nicotine addiction, and in the ability to stop smoking. Children of women who smoke during pregnancy are more likely to have low birth weights and are more likely to be nicotine or drug addicts as adults than are children who were not exposed to tobacco smoke before birth, the study found.

The team says that further studies are needed to determine whether these DNA alterations persist throughout life.

Sources: Medical Xpress; July 29, 2014; and EHP; July 2014.

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