Risk of selected birth defects by maternal residence close to power lines during pregnancy.

AIMS To evaluate selected birth outcomes from a published Norwegian cohort study in a nested case-control design with improved exposure data. METHODS Two controls matched for sex, year of birth, and municipality were selected randomly for children with the following defects: central nervous system (CNS) defects, cardiac defects, respiratory system defects, oesophageal defects, and clubfoot. The distances between maternal addresses, during pregnancy, and power lines were obtained from maps mainly of scale 1:5000. The magnetic fields in the residences were estimated based on distance, current, voltage, and configuration. RESULTS The highest increased risks were seen for hydrocephalus (OR 1.73, 95% CI 0.26 to 11.64) and for cardiac defects (OR 1.54, 95% CI 0.89 to 2.68). CONCLUSION This study does not support the hypothesis that residential exposure to electromagnetic fields from power lines causes any of the investigated outcomes.