Smoking during pregnancy may be linked to attention-deficit/hyperactivity (ADHD) in children, according to a recent study The Westside Story reported.

Researchers found that women who smoke while pregnant can increase the risk of their child developing ADHD -- a problem of not being able to focus, being overactive, not being able control behavior, or a combination of these, The Westside Story reported.

"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 in their study.

For the study, researchers collected and analyzed data on more than 84,000 born in Denmark between 1996 and 2002. When the children were y years old, mothers were of the children in the study were asked to fill out a questionnaire on their kids' behaviors, health and development. They were also interviewed about their habits during pregnancy.

Based on the findings, mothers who smoked during pregnancy are 1.6 times more likely to have a child with ADHD. If fathers also smoked during the mother's pregnancy, children were 1.8 times more likely to develop the mental disorder.

Researchers also found that children had a slightly higher risk of ADHD if their mothers used nicotine replacement therapy while pregnant. However, it was not fully proven.

"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.

Researchers noted that they did not see an association between smoking prior to being pregnant and an increased risk of ADHD in an unborn child.

The findings were recently published in the journal Pediatrics.