MONDAY, July 21, 2014 (HealthDay News) -- Children born to women
who smoked during pregnancy appear to have an increased risk of
developing attention-deficit/hyperactivity disorder (ADHD),
according to new research.
The new study also hints -- but doesn't prove -- that
nicotine-replacement products used during pregnancy, such as
patches and gum, could pose the same risk to children. Still, this
study suggests that nicotine itself, not just tobacco, may be a
hazard during pregnancy.
"We've been lulled into a false sense of security, thinking that if we can just get mothers to stop smoking and onto nicotine replacement, it will protect against any kinds of fetal damage in the developing child. This is a stark injection of reality about how that may not be the case," said Dr. Timothy Wilens, director of the Center for Addiction Medicine and acting chief of child psychiatry at Massachusetts General Hospital in Boston.
Researchers have long tried to pinpoint the hazards of smoking
during pregnancy. Among other things, lighting up during pregnancy
seems to boost the risk of miscarriage, pregnancy complications,
premature deliveries, low birth weight and even obesity in the
child's life, said study lead author Dr. Jin Liang Zhu, an
assistant professor of epidemiology at Aarhus University in
It's not clear how smoking and nicotine use in mothers may
affect the brains of developing fetuses. Zhu said nicotine may
cause abnormalities in the brain, while the products of cigarette
smoke -- such as carbon monoxide -- could affect the brain,
It's also possible that other factors are behind the association
between smoking in pregnancy and ADHD in children, the study
authors suggested. ADHD tends to run in families, and people in
families with ADHD are more likely to smoke. So, it's possible that
the association seen in this study isn't a direct cause of
expectant mothers' smoking, but may be the result of genetics or a
shared environment where smoking is present, according to
background information in the study.
ADHD is a common behavioral disorder in childhood, according to
the U.S. Centers for Disease Control and Prevention. Symptoms
include difficulty paying attention, impulsive behavior and
problems with sitting still and getting along with others.
Previous research has already linked ADHD in children to mothers
who smoked during pregnancy, noted Wilens, who was not involved
with the study.
In the new study, researchers examined the medical records of
nearly 85,000 children born in Denmark to mothers who were
recruited to be part of the study from 1996 to 2002.
Signs of ADHD were present in slightly more than 2,000 children.
The numbers were lower among kids of nonsmoking parents (1.8
percent) and in households where mom quit smoking and dad was a
nonsmoker (2 percent). The rates of ADHD were highest among kids in
families in which both parents smoked -- 4.2 percent.
Among those whose fathers didn't smoke, ADHD rates were highest
among those whose pregnant mothers were on nicotine-replacement
therapy (3.8 percent) or were smokers (3.4 percent). In households
where the father smoked and the mother was on nicotine-replacement
therapy, rates of ADHD in children were 2.9 percent, according to
The researchers cautioned that the number of pregnant mothers on
nicotine-replacement therapy in the study was small -- just 29
mothers of children with ADHD used these products during pregnancy.
As a result, "the findings are more uncertain," Zhu said. In
another caveat, the study authors noted that many parents and kids
didn't take part in a seven-year follow-up designed to monitor how
the children were doing.
Still, there are many good reasons to stop smoking before
conceiving, the experts said.
"If at all possible, try not to smoke when conceiving," Wilens said. "If you think you've conceived and you're smoking, it's best to come off cigarettes as quickly as possible. If you need to use nicotine-replacement therapy, use it for as short a time as possible."
The good news is that smoking prior to pregnancy doesn't seem to
boost the risk of ADHD in the unborn child, he said.
The study was released online July 21 in advance of publication
in the August print issue of the journal
For more about ADHD, visit the
Centers for Disease Control and Prevention.
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