Could quitting smoking during pregnancy increase the risk of a child developing attention deficit hyperactivity disorder (ADHD)? According to a new study from the Aarhus University of Denmark, there is a link between women using nicotine replacements during pregnancy, and children developing ADHD.

Previous studies have indicated that smoking during pregnancy leads to a higher risk of children developing ADHD. However, this was the first study to definitively say anything about nicotine alone.

The authors are quick to note, though, that the study does not definitively say that nicotine causes ADHD, though it is certainly a possibility. It’s also possible that it’s a case of correlation, rather than causation. Women who are more likely to have ADHD themselves, for example, might be more likely to smoke as a result of their symptoms.

For this reason, it is not possible to determine yet whether the children of women who use nicotine replacement products are more likely to develop ADHD because of their environment, or because of genetics.

The study’s researchers analyzed data from over 80,000 Danish children and their mothers in order to come to their conclusion. They talked to the mothers while they were pregnant, and then followed the children over the next 10 years to see whether they ended up with a diagnosis of ADHD. Though 2% of the children in the study ended up with ADHD, children with two smoking parents were 83% more likely to develop it, and the risk was about the same even if the mother was using nicotine replacement products.

It’s worth noting, though, that mothers who used nicotine products had babies with healthier birth weights than smokers did, so even if quitting smoking doesn’t lower the risk of ADHD development, it is positive in other ways for the developing baby.

In the U.S., more and more children have been diagnosed with ADHD over the past decade. Today, about 5% of all children are said to suffer from the disorder. For this reason, many parents are interested in any studies that can shed light on how and why the disorder develops.