Smoking during pregnancy affects the baby’s DNA, according to a study published in the American Journal of Human Genetics.
Researchers examined data from more than 6,000 mothers and their newborns and concluded that smoking influences DNA methylation — a chemical code along the DNA strand that controls when genes are activated.
The study identified 6,073 places where babies’ DNA was methylated differently compared to the babies of non-smokers. Researchers collected samples mainly from blood in the umbilical cord after delivery.
Stephanie London, co-senior author and an epidemiologist and physician at the National Institutes of Health, said the same genes were affected by the habit of smoking among adults.
‘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,’ she said.
‘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 said the study might explain the link between maternal smoking and certain birth defects and developmental conditions.
‘We already knew that smoking is related to cleft lip and palate, but we don’t know why. Methylation might be somehow involved in the process.’
We know that smoking in pregnancy is associated with adverse effects such as miscarriage of a chromosomal normal baby, low birth weight babies, stillbirth, preeclampsia, preterm rupture of membranes and preterm labour. Up until now, evidence was sparse for a persistent, demonstrable effect on the newborn.
This meta-analysis of over 6,000 individuals demonstrates that maternal smoking causes identifiable changes in foetal DNA (DNA methylation, the addition of a methyl group on to DNA strands) that persist; furthermore, these changes are associated with both childhood and developmental conditions, eg cleft palate and asthma, but also future ‘adult disease’ such as cancers associated with smoking, such as lung and colorectal cancer.