Li et al1 reported associations between prenatal exposure to magnetic fields and childhood asthma. They measured exposure to magnetic fields in pregnant women using personal monitoring and then examined their associations with newly diagnosed asthma among offspring. Each 1-mG increase in maternal magnetic field levels was associated with a 15% increased risk of asthma.
Villeneuve PJ. Exposure to Magnetic Fields During Pregnancy and Asthma in Offspring. Arch Pediatr Adolesc Med. 2012;166(1):97. doi:10.1001/archpedi.166.1.97-a