TY - JOUR T1 - Authors' response JF - Journal of Epidemiology and Community Health JO - J Epidemiol Community Health SP - 465 LP - 466 DO - 10.1136/jech.2010.132563 VL - 65 IS - 5 AU - Hozefa A Divan AU - Leeka Kheifets AU - Carsten Obel AU - Jørn Olsen Y1 - 2011/05/01 UR - http://jech.bmj.com/content/65/5/465.2.abstract N2 - We would like to thank Dr Aarstad1 for his interest in our work. We noted in the ‘Results’ section2 that the rates of cell phone use increased during the time of our study. For instance, the percentage of mothers using a cell phone during pregnancy increased from 21% to 46% from the birth years 1998 to 2001. And as stated in our conclusion, we do not rule out the possibility that uncontrolled confounding may play a role in our observed associations.Examination of heterogeneity over time within social–occupational status is presented … ER -