Pregnant women who regularly use mobile phones may be more likely to have kids with behavioral problems, especially if those children start using a phone early themselves, new research shows.
The Danish researchers studied more than 28,000 seven-year-olds and their mothers who were part of the Danish National Birth Cohort (DNBC) study.
They conclude: "Although it is premature to interpret these results as causal, we are concerned that early exposure to cell phones could carry a risk, which, if real, would be of public health concern given the widespread use of this technology."
The women in the study gave detailed information on their lifestyle, diet and environment in four phone interviews during and after pregnancy.
When their children reached the age of seven, the mothers were quizzed again about their and their kids' health and behavior, and were also asked to give details of their mobile phone use during pregnancy, as well as their kids' phone use.
The results showed that more than a third of the seven-year-olds were using a mobile phone, and 17 percent were exposed both before and after birth. Meanwhile, around three percent of children were considered to have borderline behavioural problems, with a similar number showing abnormal behaviour.
But children exposed to mobile phones before and after birth were 50 percent more likely to have problems, once other influences were taken into account.
Some might suggest that the troublesome kids were more likely to wear their parents down and get given a phone, skewing the results. However, it appears that exposure in the womb is actually the greater risk factor - and few kids start nagging quite that early.
Those exposed to mobile phones only in the womb were 40 percent more likely to have behavioral problems, while those with no prenatal exposure but with access to them by the age of seven were 20 percent more likely to exhibit abnormal behaviors.
The authors say that the new results back up their previous research.
The study appears in the Journal of Epidemiology and Community Health.