Smoking during pregnancy changes foetal DNA, says landmark study

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The study that was published in the American Journal of Human Genetics highlights the fact that smoking during pregnancy has the power to modify the foetal DNA

While science has quite substantial data on the adverse effects of smoking during pregnancy, a major study involving around 6000 women and children has given you one more reason to not smoke when you’re expecting.

What the study says

The study that was published in the American Journal of Human Genetics highlights the fact that smoking during pregnancy has the power to modify the foetal DNA. For the largest study of its kind, researchers studied data from around 6,685 newborns and their mothers around the world and were asked to fill questionnaires.

  • They were labeled as "sustained smokers", those who smoked throughout the pregnancy, "non-smokers”, those who did not smoke during their pregnancy and "any smoking", those who occasionally smoked when they were expecting.
  • Researchers then collected blood samples from the umbilical cord after delivery to analyze methylation in the baby’s DNA.
  • In the babies of mums who were "sustained smokers", the research teams identified 6,073 places where the DNA was chemically modified than in the "no smoking" infants. About half of these locations could be tied to a specific gene.

"I find it kind of amazing when we see these epigenetic signals in newborns, from in utero exposure, lighting up the same genes as an adult's own cigarette smoking. There's a lot of overlap," says co-senior author Stephanie London, an epidemiologist and physician at the National Institute of Environmental Health Sciences (NIEHS), part of the National Institutes of Health.

"This is a blood-borne exposure to smoking--the foetus isn't breathing it, but many of the same things are going to be passing through the placenta," she adds.

Even one cigarette is enough to do the damage during pregnancy

While many women might argue that they are occasional smokers and smoke only one to two cigarettes a day, the fact is that even one cigarrete is enough to do the damage.

Studies say that even light smoking is associated with lower respiratory tract infections, including a prolonged duration of respiratory symptoms (particularly cough), compromised reproductive health, an increased risk for ectopic pregnancy as well as placenta previa, and poor bone mineral density leading to frequent ankle fractures in older women.

This pictorial video shows you how toxic smoking can be during pregnancy.

Previous studies have also shown how babies behave when their mothers smoke. In one particular study, researchers found that foetuses whose mothers smoke exhibited a significantly higher rate of mouth movements than the normal declining rate of movements expected in a foetus during pregnancy.

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