Smoking during pregnancy changes a baby’s DNA, study says

We’ve known for a long time that smoking during pregnancy is a terrible thing to do. A new study is shedding light on why.

The study, published recently in the American Journal of Human Genetics, says the mechanisms for understanding exactly how maternal smoking affects the offspring have been poorly understood. What is known is that smoking during pregnancy is linked to sudden infant death syndrome, miscarriage, reduced pulmonary function, and low birth weight.

The study looked at data from 13 birth cohort studies, ultimately accessing data on 6685 newborns. 25 per cent of these newborns were exposed to at least some smoking during pregnancy and 13 per cent were exposed to sustained levels of smoking. Researchers evaluated the association between sustained smoking and differential DNA methylation. Methylation is a process by which which certain chemicals called methyl groups are added to various constituents of proteins, DNA and other molecules. The study found that chemical changes in the mother’s body activated similar responses in the fetus.

“It’s quite amazing to see these epigenetic signals in newborns exposed to tobacco in the womb, activating the same genes as those of an adult smoking,” said Dr. Stephanie London, who is an epidemiologist at the National Institute American science environmental health (NIEHS), which part of the National Institute of health. “This is a tobacco exposure through blood, the fetus does not breathe cigarette smoke but many of the effects are transmitted through the placenta.”

Despite mountains of evidence that says smoking during pregnancy is unhealthy, the message still isn’t reaching many Canadian women. A 2009–2010 Canadian Community Health Survey found that the prevalence of smoking during pregnancy could be as high as 23 per cent (other estimates peg the figure at less than 11 per cent).

A 2014 study published in the journal PLoS One revealed a strong correlation between lower socioeconomic status and smoking during pregnancy. It found that those who did not have a regular medical doctor, had a low household income, who were long-term unemployed, had less than a university education, were not living as a couple and were under 25-years old, all had higher rates of smoking while pregnant.

Smoking also varies greatly by region in Canada. According to Statistics Canada, Nunavut has Canada’s highest overall smoking rate, at 62 per cent. And Frankie Best, a tobacco reduction specialist with the Government of Nunavut, says she has heard anecdotal evidence from community health staff that suggests more than 90 per cent of pregnant women smoke there.

Another recent study sheds light on just how addictive nicotine can be, and suggests that more may need to be done from a public policy perspective. The study, published in March in the journal Addiction, found that 43 per cent of women who stopped smoking for their pregnancy started smoking again within six months of childbirth.

“Most pregnant smokers do not achieve abstinence from smoking while they are pregnant, and among those that do, most will restart smoking within six months of childbirth,” the study’s authors said. “Our report reveals a wide gulf between what pregnant women need to quit smoking and what our healthcare services currently provide,” they wrote.

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