Vrijheid M, Martinez D, Forns J, Guxens M, Julvez J, Ferrer M, Sunyer J. Prenatal Exposure to Cell Phone Use and Neurodevelopment at 14 Months. Epidemiology. Jan 16, 2010 Ahead of print.
Recently, an association was reported between prenatal and, to a lesser extent, postnatal exposure to cell phones and behavioural problems in 7 year old children. Because fetal exposure to electromagnetic fields from cell phones is extremely low, a direct biological effect is unlikely to explain these findings. The results of this study could be biased by errors in reporting exposure or outcome or by unmeasured confounding factors. The authors, therefore, caution against a causal interpretation of their finding.
The objective of this study was to examine the relationship between cell phone use during pregnancy and neurodevelopment at 14 months of age using the data from a prospective birth cohort study.
A population-based birth cohort established in Sabadell (Spain) included women who visited the primary healthcare center of Sabadell for a first trimester ultrasound between July 2004 and July 2006. Of the 1,009 eligible women, 657 (60%) agreed to participate. Information on education, social class, maternal health and obstetric history, lifestyle and environmental factors was obtained from a questionnaire. The questionnaire completed in week 32 of pregnancy contained questions on cell phone use; 587 women answered these questions. Mental and psychomotor development was assessed at the age of 14 months (range 12-17 months) for 530 children using the Bayley Scales of Infant Development. The assessment was conducted by 2 psychologists who were unaware of any exposure information.
Of the 530 mother-child pairs with information on prenatal phone use and Baley scale assessments, 61 mothers did not use cell phone, 162 mothers made 1 call a day, 239 mothers – 2-4 calls, and 68 mothers – 5 calls or more. Compared to non-users, children of cell phone users tended to have higher Baley mental score and lower Baley psychomotor score. Within users, there was no trend in mental or psychomotor scores with the level of cell phone use.
The design of this study eliminates the possibility of recall bias related to outcome. Though random errors in reporting cell phone use are likely, self-reported numbers of phone calls are expected to be reasonably accurate. The observed small differences in neurodevelopment scores between children of cell phone users and children of non-users may be explained by the very small number of mothers who did not use cell phones and by residual confounding by factors related to mobile phone use/non-use. The results of this study should not be extrapolated beyond the age of 14 months. Because the number of heavy users was small, these findings cannot exclude effects of very heavy cell phone use.
The findings provide little evidence for an early adverse neurodevelopmental effect of maternal cell phone use during pregnancy.