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 Researchers analyzed data on mothers and their newborn children to
see how smoking influences DNA methylation, a chemical code along
the DNA strand that controls some DNA mechanics and when genes get
activated. Whether certain points along the DNA molecule are
methylated or not can determine everything from eye color to a
person's predisposition to certain diseases.
When women smoked daily during pregnancy, researchers identified
6,073 places where their babies’ DNA was methylated differently from
the DNA of nonsmokers’ infants.
Many of the differences were found on or near a collection of genes
related to lung and nervous system development, smoking-related
cancers and birth defects such as cleft lip and palate.
“We already knew that smoking during pregnancy, or after the child
is born, is to be avoided at all costs,” said senior study author
Dr. Stephanie London, deputy chief of the epidemiology branch at the
National Institute of Environmental and Health Sciences in Research
Triangle Park, North Carolina.
“This study provides more evidence – signals you can see at birth
that are similar to signals you can see in adult smokers,” London
added by email.
Researchers pooled results from 6,685 mothers and their newborns
from studies performed around the world.
Most of the women said they didn’t smoke, but about 13 percent of
the women were daily smokers and another 25 percent admitted to
occasional smoking during pregnancy.
To analyze methylation patterns in newborns’ DNA, researchers
collected samples mainly from blood in the umbilical cord after
delivery. In addition to documenting differences between the infants
of nonsmokers and regular smokers, the researchers looked at a
smaller group of older children and found that at least some of the
smoking-related methylation differences in the children of mothers
who were smokers during pregnancy persisted.
While the study doesn’t prove how maternal smoking may influence
child development or disease, the findings suggest that DNA
methylation differences might be involved in the appearance of
certain birth defects or medical problems in babies born to mothers
who smoke, the authors conclude in The American Journal of Human
Genetics.
It’s possible that smoking during pregnancy might hijack systems in
babies that determine how DNA is deployed and alter programs in the
cells in a way that impacts future health, said Andrea Baccarelli,
an environmental epigenetics researcher at Harvard University in
Boston, who wasn’t involved in the study.
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It’s also possible that programs in the cells might change to adapt
in response to smoking to cope with its adverse effects, Baccarelli
added by email.
“I have likened this to a musical score, where the DNA is the score
itself,” Baccarelli said. “You can imagine how the performers, in
advance of the premier, might add marks to the score. They don’t
modify the score, but they modify the way the score is executed.”
Even if the reasons for these cellular changes aren’t certain, the
message for patients is clear, said Paul Fowler, a director of the
Institute of Medical Sciences at the University of Aberdeen in the
U.K.
“Everybody should know by now that smoking while pregnant is bad for
the baby,” Fowler, who wasn’t involved in the study, added by email.
“What this new study does is so strongly reinforce that message that
there can be long-term consequences for their babies after birth.”
Women who don’t quit before conception still have a chance to
improve their baby’s health, noted Dr. Amanda Drake, a
cardiovascular and pediatric health researcher at the University of
Edinburgh and the Royal Hospital for Sick Children in the U.K.
“Sustained smoking leads to more effects,” Drake, who wasn’t
involved in the study, said by email. “Even if women do not stop
smoking before conception, stopping smoking during pregnancy is
still better than continuing throughout.”
SOURCE: http://bit.ly/1p2sByx The American Journal of Human
Genetics, online March 31, 2016.
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