In the study, slated for publication in the July issue of the journal Epidemiology, researchers at the Universities of California, Los Angeles, and Aarhus, Denmark, issued a survey to mothers of 13,159 children in Denmark. The survey asked the mothers questions about their use of cell phones during their pregnancy as well as their child's behavior and their current cell phone use.
The researchers found that the mothers who said they used cell phones during their pregnancy also reported a higher level of behavioral problems in their children.
But while the results suggested an increased risk of hyperactivity, impulsivity and difficulty concentrating in children whose mothers used cell phones during pregnancy, epidemiological experts -- including one of the paper's authors -- said it would be a mistake to assume that the findings were conclusive.
In fact, Dr. Jorn Olsen, professor and chair of epidemiology at UCLA and a co-author of the paper, said media coverage of the research thus far has been off target.
Olsen specifically referred to a report in the British press with the headline "Warning: Using a Mobile Phone While Pregnant Can Seriously Damage Your Baby."
"That's clearly not what we wanted to suggest, and we think that there is no reason that pregnant women should be very alarmed at the findings we have," Olsen said.
He added that he and his colleagues had not expected the paper to be released until next month.
"I think that a number of journalists broke the story on this and that they did not take all of the assumptions into consideration [when reporting it]," he said.
Charles Poole, associate professor of epidemiology at the University of North Carolina at Chapel Hill, said that a number of factors could have been at play in this preliminary study that would have thrown the results off one way or the other.
He said one problem was that the information was obtained through interviews with the mothers, who may not have given accurate accounts of their cell phone use when pregnant. Alternatively, he noted, perhaps mothers who were heavy users of cell phones were more likely to report behavior problems in their children.
Additionally, the authors "only briefly mentioned the possibility that maternal cell phone use, especially postnatal use, could have adverse effects on child behavior in ways having nothing at all to do with radio frequency fields," he said. One possibility: Mothers who were constantly on their cell phones may have paid less attention to their children, who subsequently acted out.
Olsen added that the study was never intended to suggest a biological mechanism by which cell phone exposure could lead to behavioral problems in children.
"I don't think anyone has suggested that there is a causal mechanism," he said.
And in the study, the authors point out other confounding variables that could explain behavioral changes in these children, including diet, exposure to lead paint and exposure to pollution.
"We think it is interesting, but many associations seen in studies of this type occur due to chance," Olsen said, adding that parents can comfort themselves with the fact that the vast majority of children who have been exposed to cell phones, both in and out of the womb, do not exhibit behavioral problems.
The study is far from the first to attempt to explore some of the possible adverse health effects of cellular phones. And, as with past studies, the conclusion of this most recent study is that more research is needed in order to determine whether there is anything to be worried about.
"Current scientific evidence doesn't indicate any adverse health outcomes associated with exposure to radio frequency energy from cell phones," said U.S. Food and Drug Administration spokeswoman Peper Long, who agreed that the public should be cautious in interpreting the most recent study.
"Although there have been reports of negative health effects from low levels of radio frequency energy, these reports have not been replicated or confirmed," she said.
Solid Answers? Please Hold
Olsen noted that there are many reasons to explore all conceivable health impacts of cell phone use, as it is a technology that is becoming ever more pervasive in our highly connected society. The results of the study, Olson said, could provide avenues to other researchers studying the potential effects of cell phone radiation.
Still, epidemiological experts said, the findings may not be ready for public consumption.
"I think this is a competently and well-done study, but I think there are enough red flags that this should probably not be something the U.S. public needs to be alarmed about," said Dr. Tim Byers, professor of epidemiology and community health at the University of Colorado in Aurora. "I am particularly concerned about mothers and fathers who may constantly be worried about whether something they did caused their child's behavioral problems."
"This study is well worth publishing [in a medical journal]," Poole said. "But, given its highly preliminary and unexpected nature, and its liability to any number of methodologic problems, it is not the kind of study that should be making news in the general public.
"No one connected with the study should be doing anything to encourage media attention on it -- that includes the journal, the funding source, the institutions with which the authors are affiliated and the authors themselves," Poole added. "In my opinion, that would constitute sensationalism."