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Expecting mothers are told to be especially careful during pregnancy—and not without reason. There are many foods, chemicals and activities that might harm a fetus. The science behind the restrictions that pregnant women religiously observe stems from tangible studies. Researchers from Johns Hopkins Bloomberg School of Public Health recently found that traces of the mother’s smoking during her pregnancy may affect a child for years. The study, which was published in the Environmental Research journal, compared the blood of 531 preschoolers from six different places in the US to their mothers’ smoking habits and found a striking correlation between the two. Rather than create direct changes to the sequence of the DNA, smoking causes changes in the epigenetic memory of DNA, or the way that DNA is expressed. These changes are passed down to children. Epigenetic factors sit on top of the DNA and make modifications to the activity of a cell’s DNA, turning certain genes on or off. Examples of epigenetic memory include DNA methylation and histone modification. Using patterns in changes in 26 locations of the genome in the children’s blood samples, they could predict whether the mother smoked 81% of the time.

 Smoking has many other consequences, including effect on unborn children.

Image Source: Christopher Furlong

Although the new study’s findings may also be related to second-hand smoke exposure after birth rather than smoking during the pregnancy itself, the evidence from past studies suggests that smoking during the pregnancy partially contributes to the changes in the children’s expression of DNA. The Johns Hopkins researchers say that the significance of the study lies in its implications for the effects of other materials on children in the womb. Exposure to toxins from plastics or from drinking water while in the womb might have similar genetic on children. These, in turn, might be linked to diseases like obesity, heart disease and autism. While exposure to smoking during pregnancy is relatively easy to measure compared to exposures to other toxins the mother may not know about, the study’s findings give clues towards explaining how exposure to these other toxins might affect children years after birth. Future research, keeping in mind the study’s results that exposure to toxins before birth can affect children, could help scientists learn more about dangerous toxins for pregnant women. By focusing greater efforts towards measuring how other toxins might affect children after birth, scientists can make the world safer for children.

Feature image source: smoke by Anastasia Massone 

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