Pregnant women who quit smoking may spare their children emotional problems, a new study from the Netherlands suggests.
Researchers in looked at brain scans and the emotional well-being of 6-year-olds, including 113 kids who were not exposed to tobacco, and 113 kids whose mothers smoked during pregnancy. Of those women who smoked during pregnancy, 17 quit smoking early on.
They found that children exposed to tobacco throughout pregnancy had smaller brains, and the cortex of the brain was thinner in certain regions, compared with children whose mothers did not smoke during pregnancy. The children whose mothers smoked also showed more emotional problems, such as depression symptoms and anxiety.
But the researchers also found that children whose mothers quit once they learned they were pregnant did not show reduced brain volume or more emotional problems, compared with the children whose mothers didn't smoke at all.
"Importantly, brain development in offspring of mothers who quit smoking during pregnancy resembled that of [children who were not exposed to tobacco]," the researchers wrote in their study, published today (Oct. 7) in the journal Neuropsychopharmacology.
Previous studies have shown that smoking during pregnancy has negative effects on a baby's health — it may restrict the growth of the fetus, and may increase the risk of stillbirth and preterm birth. [7 Ways Pregnant Women Affect Babies]
In the United States, prevalence of smoking among pregnant women has declined over the years. In the year 2000, 12 percent of pregnant women smoked, down from 25 percent in 1980.
In the study, the researchers found that the thickness of the superior frontal cortex was linked with mood problems in the children whose mothers continued smoking. This brain area has been implicated in the regulation of mood states in past studies.
It is not clear how being exposed totobacco during pregnancy influences brain development, the researchers said. However, evidence from animal studies suggests that nicotine can induce changes in levels of neurotransmitters, the signaling chemicals in the brain.
Another potential mechanism may be that nicotine affects neurons' ability to find their correct places during early brain development, the researchers said.
It is also possible that the narrowing of blood vessels in smoking mothers reduces blood flow and oxygen to the fetus. This decreased nutrient and oxygen supply might induce long-lasting effects on brain structure, the researchers said.
The study had its limitations, the researchers said. The number of mothers who quit smoking during pregnancy was low, so the results should be interpreted with caution, they said. Also, the study found an association, and cannot prove a cause-and-effect link between quitting smoking and a reduced risk of emotional problems.
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