NEW YORK (Reuters Health) – Children whose mothers used cellphones frequently during pregnancy and who are themselves cellphone users are more likely to have behaviour problems, new research shows.

The finding "certainly shouldn't be over interpreted, but nevertheless points in a direction where further research is needed," Dr. Leeka Kheifets of the UCLA School of Public Health, who helped conduct the study, told Reuters Health. "It's a wonderful technology and people are certainly going to be using it more and more," she added. "We need to be looking into what are the potential health effects and what are ways to reduce risks should there be any."

Kheifets 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 seven, mothers were asked to complete a questionnaire about their children's behavior and health, as well as the mother's own cellphone use in pregnancy and the child's use of cellphones. 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 cellphone 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 foetus's exposure to radiofrequency fields by a mother's cellphone use is likely very small. However, they add, research has shown that children using cellphones are exposed to more radiofrequency energy than adults, because their ears and brains are smaller.

Because cellphone use was so infrequent among children in the study – 30 percent of kids were using a cellphone, but just one percent used a cellphone for more than an hour a week – radiofrequency exposure seems unlikely to have caused any behavior problems, they say. "Another possible explanation for the observed association might be the lack of attention given to a child by mothers who are frequent users of cellphones," the researchers suggest. They note that mothers who used cellphones frequently were of lower socio-occupational status, more likely to have mental health and psychiatric problems, and more likely to have smoked while they were pregnant.