Magnetic Field Exposure during Pregnancy Increases Risk of Developing Asthma

by Dr Sam Girgis on August 1, 2011

Exposure to magnetic fields that are produced by power lines, electronics, and cell phone towers has been suggested to be linked to several health problems.  Researchers from the Kaiser Foundation Research Institute, lead by Dr. De-Kun Li, have found that in utero exposure to magnetic fields increases the risk of developing asthma in the unborn child.  The results of the research were published online in the journal Archives of Pediatric and Adolescent Medicine.  The researchers used data from a prospective cohort study using mother child pairs performed at Kaiser Permanente Northern California.  In the study, the mothers carried a meter that was designed to measure magnetic field exposure during a 24 hour period during the first or second trimester of pregnancy.  The researchers adjusted for confounding factors such as age, race, education, smoking during pregnancy, and maternal history of asthma.  The children were followed up for as long as a 13 year period and about 20% developed asthma (130 of 626 children).  The researchers found a statistically significant linear dose response relationship between maternal magnetic field exposure and the risk of developing asthma in their offspring.  For every 1 milligaus increase in magnetic field exposure to the mother during pregnancy there was an associated 15% increased risk of developing asthma in their offspring.  Children of mothers with the highest magnetic field exposure had more than 3.5 fold increased rate of childhood asthma compared to children of mothers with the lowest exposure to magnetic fields.  In addition, there was also a statistically significant association observed for birth order and maternal history of asthma.  Firstborn children had higher risk, and children of mothers with a history of asthma had higher risk of developing asthma when mothers were exposed to magnetic fields during pregnancy.  The authors wrote, “Our findings provide new epidemiological evidencethat high maternal [magnetic field] levels in pregnancy may increase the riskof asthma in offspring… the findings of the present study open up a new area in understanding the risk factors for asthma and the health effects of ubiquitous [magnetic field] exposure, especially during pregnancy”.  The findings of the study need to be replicated, but will undoubted cause increased controversy in the debate about the placement of power lines and cell phone towers.


De-Kun Li et al. “Maternal Exposure to Magnetic Fields During Pregnancy in Relation to the Risk of Asthma in Offspring” published online August 1, 2011 Arch Pediatr Adolesc Med doi:10.1001/archpediatrics.2011.135

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{ 5 comments… read them below or add one }

Chris Bergstrom August 2, 2011 at 10:41 am



Dr Sam Girgis August 2, 2011 at 9:41 pm

The exact mechanism is unclear, but it likely has to due with the effects of magnetic fields on the developing lungs of the baby in utero.


Bob August 2, 2011 at 6:35 pm

More magnetic fields in a location will tend to be associated with more solder, more hot electrical insulation, more hot motor and transformer cores, more ozone from sparking, etc. Until I am convinced that they adjusted for all of these, I am not going to get overly excited about magnetic fields per se.


Chris Bergstrom August 3, 2011 at 11:50 am

I suppose since we know EM radiation has effects on tissue, it’s not too much of a stretch to think a magnetic field might. But also, what Bob says makes a lot of sense – correlated factors could be responsible. Thanks to you both for your answers – I’m going to chew on this idea today.


Lisa the Magnetic Woman November 7, 2011 at 1:14 am

This is interesting but how will it apply to life in practic? I mean, how can a pregnant woman guard herself from harming her baby by exposure to magnetic fields? It could be the top of an ice berg as far as I can see… Thanks for an interesting post! Lisa


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