Smoking in pregnancy alters baby’s DNA

Smoking while pregnant causes chemical changes to the DNA of the unborn baby that may predispose them to lifelong health conditions, research shows.

Changes in the chemical structure of the foetus’ DNA can be detected from as early as 12 weeks into pregnancy, according to the research.

The findings add significant weight to existing knowledge of the dangers of smoking while pregnant and show that risks may be greater than previously thought.

Crucial changes

Researchers from the Universities of Edinburgh, Aberdeen, Glasgow and Nottingham showed that maternal smoking leads to crucial changes in chemical tags known as ‘epigenetic marks’, which are normally attached to DNA.

These epigenetic marks, known as DNA methylation, can affect how genes function. The researchers were able to show for the first time that such changes are present in the livers of unborn children from between 12 and 20 weeks of pregnancy.

These early changes in DNA methylation may mean the baby is more susceptible to a range of diseases in future.

Disease risk

It is the first time such changes have been detected so early in pregnancy. The study demonstrates another way in which the burden of maternal smoking persists into adulthood, the researchers say. Babies born to smoking mothers are more likely to grow up to be obese and diabetic, they add.

From as early as the second trimester, a baby whose mother smokes is at an increased risk of developing obesity, cardiovascular disease, cognitive problems and asthma and this risk lasts throughout life. The liver is a key metabolic target tissue and changes here are likely to have a direct effect on foetal development and long-term health.

Maternal smoking

Despite current health warnings, it is estimated that the prevalence of smoking during pregnancy remains high. In developed countries up to 25 per cent of pregnant women smoke and fewer than 4% stop smoking while pregnant.

This [study] is significant because a worryingly high number of women will continue to smoke during pregnancy and the observed effects of DNA methylation may become amplified with ongoing exposure to cigarette smoke in the womb.

Gender differences

The study also showed that maternal smoking affected normal differences in tissues and organs between the sexes, which are known to be important for good health.

Our study also detected important sex differences in foetal liver function. We found that exposure to maternal smoking resulted in the livers of male foetuses becoming more like female livers and vice-versa.

The research is published in the journal BMC Medicine. It was funded by the Medical Research Council, Chief Scientist Office Scotland, the European Community’s Seventh Framework Programme and NHS Grampian Endowments.