Pregnant women who regularly use mobile phones are more likely to have children with behavioral problems, according to a study by a UCLA researcher who had previously written there was no proof of "any adverse health effect."

Mothers who used their mobile phone while pregnant were 54 percent more likely to report issues such as hyperactivity and emotional problems in their children, Britain's Daily Mail and The Independent reported Monday.

The study was conducted by researchers at UCLA and a university in Aarhus, Denmark. The findings will be published in the July issue of the journal Epidemiology.

Dr. Manny Alvarez, managing health editor for FOXNews.com, said there is no need for pregnant women to be alarmed over this study yet.

"This study in its current form fails to link a direct cause and effect between cell phone use in learning disabilities in children," Alvarez said. "What you have in the study is an epidemomology survey where the use of cell phones seem to be more frequent in women whose children have learning disabilities."

UCLA Professor Leeka Kheifets, who had previously been skeptical of reports linking mobile phone use to behavior disorders in children, concluded with her three co-authors that there did appear to be an association between mobile phone exposure and behavioral problems. However, they said, radiation may not be the cause.

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The researchers said there may be other possible explanations for the rise in behavioral problems, including that mothers who were frequently on the phone through pregnancy might continue the pattern after birth and spend less time with their babies.

Using a mobile or cell phone two to three times a day was enough to raise the risk of behavioral problems in children, and letting children under the age of 7 use a mobile phone also put them in danger, the study of more than 13,000 women found.

The study follows a finding by the official Russian radiation watchdog that the danger posed by mobile phones is "not much lower than the risk to children's health from tobacco or alcohol."

The UK's Health Protection Agency said the study's findings were unexpected and highlighted the need for caution over mobile phones. But it stopped short of telling pregnant women not to use them.

"Its findings need to be investigated thoroughly. There may be another cause for the effect observed," a spokesman said.

"There is still no data available yet that has measured the radiation exposure to the acutal fetus from the cell phone," Alvarez said.

Alvarez said he believes there are other environmental impacts that are far more detrimental to prengant women, such as mercury, lead exposure and biological contaminants in food.

Click here to read the report in the Daily Mail.

Click here to read the report in The Independent.