Epidemiological study (observational study)

Exposure to Magnetic Field Non-Ionizing Radiation and the Risk of Miscarriage: A Prospective Cohort Study. epidem.

By: Li DK, Chen H, Ferber JR, Odouli R, Quesenberry C

Published in: Sci Rep 2017; 7 (1): 17541

Aim of study (acc. to author)

A prospective cohort study was conducted in the USA to examine the association between exposure to magnetic fields during pregnancy and the risk of miscarriage.

Further details

Measurement days were divided into typical days (measurements were conducted during a typical day of the pregnancy) and non-typical days based on the participants' diaries.

Endpoint/type of risk estimation

reproductive effects and pregnancy outcomes: miscarriage

Exposure

Assessment

dosimeter: 24 hours exposimeter measurement of magnetic flux density
questionnaire: diary of activities on the measurement day
list

Exposure groups

Reference group 1	99th percentile of exposure: < 0.25 µT (1st quartile)
Group 2	99th percentile of exposure: ≥ 0.25 µT
Reference group 3	99th percentile of exposure, typical day: < 0.25 µT (1st quartile)
Group 4	99th percentile of exposure, typical day: 0.25 - 0.36 µT (2nd quartile)
Group 5	99th percentile of exposure, typical day: 0.37 - 0.62 µT (3rd quartile)
Group 6	99th percentile of exposure, typical day: > 0.63 µT (4th quartile)

Population

Group:
- women
- children in utero
Age: ≥ 18 years
Characteristics: pregnant women with gestational age at pregnancy test of 10 complete weeks or less
Observation period: not stated
Study location: USA (San Francisco Bay Area)
Data source: cohort of Kaiser Permanente Northern California, USA

Study size

Total	1,627
Participants	1,054
Evaluable	913

Statistical analysis method:

Cox proportional regressions analysis

( adjustment:

education
maternal age, race, smoking since last menstrual period, prior miscarriage. Further adjustment for maternal nausea/vomiting, maternal income, marital status, alcohol use, caffeine intake, maternal fever, vaginal bleeding, urinary tract infection, carrying loads > 4.5 kg, exposure to solvents or degreasers, vitamin intake and Jacuzzi/hot tub/steam room/sauna use during pregnancy

)

Conclusion (acc. to author)

Women who were exposed to magnetic flux density ≥ 0.25 µT levels had an increased risk of miscarriage (HR 2.72, CI 1.42–5.19) compared to women with lower exposure (< 0.25 µT). The increased risk of miscarriage associated with high magnetic flux density was consistently observed regardless of the sources of high magnetic fields. The association was much stronger in the subgroup with measurements on a typical day of participants’ pregnancies. The finding also demonstrated that accurate measurement of exposure to magnetic fields is vital for examining health effects of magnetic fields.
The authors conclude that the study provides fresh evidence, directly from a human population, that exposure to magnetic fields could have adverse biological impacts on human health.

Study funded by

National Institute of Environmental Health Sciences (NIEHS), North Carolina, USA

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