The use of electric bed heaters and the risk of clinically recognized spontaneous abortion.
We conducted a prospective cohort study to evaluate the relation of spontaneous abortion and electric bed heater use during the first trimester of pregnancy. Compared with non-users, rates of spontaneous abortion were lower for women who used electric bed heaters. The adjusted odds ratio and 95% confidence interval (CI) for the two major devices used, electric blankets (N = 524) and waterbeds (N = 796), were, respectively, 0.8 (95% CI = 0.5-1.1) and 0.9 (95% CI = 0.7-1.2). An increase of risk with increasing intensity (setting-duration combination) of use was not observed. Users of electric blankets at low settings for most of the night (N = 171) had lower risks of spontaneous abortion than non-users (adjusted odds ratio = 0.5; 95% CI = 0.3-1.0). Twenty women who used electric blankets at a high setting for 1 hour or less had an adjusted odds ratio of 3.0 (95% CI = 1.1-8.3), but we found no spontaneous abortions among the few women (N = 13) who used a high setting for 2 or more hours. We found that exposure rankings of the magnetic field time-weighted average and a rate of change metric did not correspond monotonically to the pattern of spontaneous abortion risks and that electric blankets contribute less to overnight time-weighted average magnetic fields than has been thought.
Lee
G M
GM
Environmental Health Investigations Branch, Department of Health Services, Oakland, CA 94612, USA.
Neutra
R R
RR
Hristova
L
L
Yost
M
M
Hiatt
R A
RA
D000022:Abortion, Spontaneous / Q000453:epidemiology / Q000209:etiology*; D000293:Adolescent; D000328:Adult; D001512:Bedding and Linens; D015331:Cohort Studies; D004574:Electromagnetic Fields / Q000009:adverse effects*; D005260:Female; D006361:Heating / Q000009:adverse effects*; D006801:Humans; D016017:Odds Ratio; D011247:Pregnancy; D011256:Pregnancy Outcome; D011261:Pregnancy Trimester, First; D018570:Risk Assessment