Grand Rounds

Is There a Relationship between Magnetic Field Radiation and an Increased Risk of Miscarriage?

BACKGROUND AND PURPOSE:

Everyone is exposed to magnetic field (MF) non-ionizing radiation
Traditional sources include power lines, appliances and transformers
Newer sources include wireless networks, cell towers and cell phones
The International Agency for Research on Cancer (IARC) has classified MF as a possible carcinogen
Li et al. (Scientific Reports, 2017) sought to determine whether there is an association between exposure to MF and miscarriage risk

Prospective cohort study
Research included pregnant members of the Kaiser Permanente Northern California (San Francisco Bay area) system
Positive pregnancy tests were used to ensured early recruitment
- Women <10 weeks gestation were eligible
MR measurements
- Study focused on high levels of MF exposure
  - 99th percentile of MF measurements during the 24 hour period was used to classify exposure level
- Women carried a meter for 24 hours on a typical day (measures MF in milligauss [mG])
- Low MF exposure: 99th percentile of MF exposure levels was in the lowest quartile (<2.5 mG)
- Higher three quartiles were classified in the high MF exposure group
Women kept a diary so that researchers could
- Identify locations
- Verify that activities were typical
- Examine if locations/activities were associated with higher MF exposure
An in-person interview was conducted with all participants to ascertain potential confounders, including pregnancy history and risk factors for miscarriage
Results adjusted for maternal age at interview, race, education, smoking since LMP and prior miscarriage
Additional variables used for adjustments included maternal nausea/vomiting, maternal income, marital status, alcohol use, caffeine intake, maternal fever, vaginal bleeding, urinary tract infection, carrying loads > 10lbs, exposure to solvents or degreasers, vitamin intake and Jacuzzi/hot tub/steam room/sauna use during pregnancy

Among 1,627 eligible women, 1,054 participated
After controlling for confounders and using data from a typical day, women who were exposed to higher levels of MF had 2.72 times the risk of miscarriage (hazard ratio = 2.72, 95% CI: 1.42–5.19) 
There was no dose-response observed above 2.5 mG
This association was conserved despite location and source of high MF
The correlation was stronger if MF was measured on a typical day of participants’ pregnancies

These results support previous publications that noted an associated between high MF levels in pregnancy and increasing risk of miscarriage
Lack of dose-response may be related to threshold radiation effects
This study identified an almost 3-fold increase in miscarriage risk, independent of sources or locations

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