New research published in July 2008 in the journal Epidemiology showed that children whose mothers used cell phones frequently during pregnancy and who are themselves cell phone users are more likely to have behavior problems.

The author of the study and her team looked at a group of 13,159 children whose mothers had been recruited to participate in the Danish National Birth Cohort study early in their pregnancies. When the children reached age 7, mothers were asked to complete a questionnaire about their children’s behaviour and health, as well as the mother’s own cell phone use in pregnancy and the child’s use of cell phones.

After the researchers adjusted for factors that could influence the results, such as a mother’s psychiatric problems and socioeconomic factors, children with both prenatal and postnatal cell phone exposure were 80 percent more likely to have abnormal or borderline scores on tests evaluating emotional problems, conduct problems, hyperactivity, or problems with peers.

Risks were higher for children exposed prenatally only, compared with those exposed only postnatally, but were lower than for children exposed at both time points.

Kheifets and her colleagues note that a fetus’s exposure to radiofrequency fields by a mother’s cell phone use is likely very small. However, they add, research has shown that children using cell phones are exposed to more radiofrequency energy than adults, because their ears and brains are smaller.

Because cell phone use was so infrequent among children in the study - 30 percent of kids were using a cell phone, but just 1 percent used a cell phone for more than an hour a week - radiofrequency exposure seems unlikely to have caused any behavior problems, they say.

Kheifets and her team believe that while their findings are preliminary, they should be reported. "We felt that the public is quite capable of dealing with proper information," the researcher said. "One shouldn’t really try to be paternalistic about it."