For years, doctors have been urging women who get pregnant to give up cigarettes due to the many serious dangers that they pose to unborn babies and pregnant women. In the age of nicotine patches and nicotine gum, some physicians have even advised expecting women to switch to these, as they are believed to be less harmful to the baby than cigarette smoke.
But that may not be the case when it comes to attention-deficit/hyperactivity disorder in children.
A new study from Aarhus University in Denmark found that nicotine-replacement products are associated with about the same risk of having a child with ADHD as when the mother smokes cigarettes during her pregnancy. This could mean that nicotine itself, not just the smoke and many other chemicals in tobacco smoke, may be a danger for the baby.
Scientists have known for decades that when a woman smokes cigarettes during pregnancy, she increases her risk of miscarriage, pregnancy complications, premature birth and low birth weight. Much of the risk is the result of decreased oxygen and blood flow to the fetus (carbon monoxide particles in cigarette smoke bind to oxygen-carrying hemoglobin molecules in the blood, making it harder for hemoglobin-bearing cells to deliver their oxygen cargo).
But researchers are unclear about the ways in which smoking and nicotine may affect the brains of developing babies. It’s possible that the chemicals themselves, as well as byproducts of cigarette smoke like carbon monoxide, both may cause abnormalities or adverse effects in the baby’s brain, according to Dr. Jin Liang Zhu, assistant professor of epidemiology at Aarhus University.
It is also possible that other factors may be involved in the connection between smoking or using nicotine products, and ADHD. For example, the researchers offered, ADHD has a tendency to run in families, and people in families with ADHD are more apt to be smokers. So, perhaps the increased risk of ADHD in children of mothers who smoke or use nicotine products reflects not only maternal habits but environmental exposures at home, as well as genetics.
Previous studies had linked ADHD in children with maternal smoking during pregnancy.
For the current study, researchers analyzed medical records of close to 85,000 children born in Denmark to mothers who signed up for the study from 1996 to 2002. ADHD symptoms were present in more than 2,000 children.
Among non-smoking parents, 1.8 percent of children had ADHD symptoms; in families where mothers had quit smoking and fathers were non-smokers, 2 percent of children had ADHD symptoms. The percentage of children with ADHD was highest among parents who were both smokers, at 4.2 percent.
In families where fathers didn’t smoke, ADHD rates were highest when pregnant mothers were on nicotine-replacement therapy, at 3.8 percent, or when mothers smoked, at 3.4 percent. In homes where the father smoked and the mother was on nicotine-replacement therapy, ADHD rates in children were 2.9 percent.
Smoking before pregnancy did not appear to increase the risk of ADHD in the child.
Results of the study were published online in July, 2014 in the journal Pediatrics, and in the August, 2014 print version of the journal.
By Lisa Pecos