(RxWiki News) It's pretty common knowledge that smoking isn't good for you, and smoking during pregnancy isn't good for either of you.
A new study adds to that knowledge with more information on the risks of attention deficit hyperactivity disorder (ADHD) in children of mothers who smoked during pregnancy.
Children were more likely to have ADHD if both their parents smoked than if neither parent smoked.
But the risk was especially linked to smoking in children's mothers during pregnancy.
"Don't smoke while pregnant."
The study, led by Jin Liang Zhu, PhD, of the Research Program for Children’s Mental Health at Aarhus University in Denmark, aimed to better understand the link between ADHD and smoking during pregnancy.
The authors analyzed data on 84,803 children born in Denmark between 1996 and 2002.
The mothers of the children had been recruited for the study during pregnancy and participated in four telephone interviews, which included asking questions and their and their partners' smoking.
Then, when the children were 7 years old, the parents filled out a follow-up questionnaire about the child's health, development and behavior based on established psychology assessments.
The behavior questionnaire included questions related to attention deficit and hyperactivity behaviors.
In addition, the researchers had access to information through various national registries on which children had been officially diagnosed with ADHD.
Overall, 2.4 percent of the children had been diagnosed with ADHD or received ADHD medication during follow-up.
The researchers found that smoking among the mothers and the fathers appeared to increase the risk of an ADHD diagnosis or medication prescription for the children.
However, a mother's smoking had a much greater association with ADHD than a father's smoking.
For example, before adjustments had been made for demographic characteristics, children born to only a mother who smoked were 1.6 times more likely to have ADHD than children born to nonsmoking parents.
If the father also smoked, that risk increased to 1.8 times the risk of a child with nonsmoking parents.
After accounting for differences among the children in demographic characteristics, children were 1.3 times more likely to have ADHD if their mother smoked than if they had been born to nonsmoking parents.
The researchers also found a slightly higher risk of ADHD in mothers who used nicotine replacement therapy while pregnant, though this risk was smaller.
Further, children born to smoking fathers (but not mothers) also had a slightly increased risk of ADHD, which increased if the mother had previously smoked and quit.
"Our findings suggest that exposure to prenatal tobacco smoke, possibly nicotine, may have a prenatal programming effect on the risk of ADHD in children," the authors wrote.
Alternatively, the authors said that other factors related to the family or household might also play a role in the ADHD risk.
Regardless, women should not smoke while pregnant, according to Andre Hall, MD, an OBGYN at Birth and Women's Care, PA in Fayetteville, NC.
"The prenatal period is a time of programming and organ development that is affected by a host of environmental influences," Dr. Hall said. "Smoking has been widely determined to have adverse effects on the development of the unborn child. There are absolutely no positive effects on the fetus caused by smoking."
The study was published July 21 in the journal Pediatrics. The research was funded by the Tryg Foundation and the European Research Council. The authors reported no conflicts of interest.