A study of the incidence of spontaneous abortions among video display terminal (VDT) users was conducted. The cohort consisted of 2118 female directory assistance operators employed at two telephone companies in the southeastern United States who used VDTs. The comparisons consisted of 2128 general operators at the same companies who did not use VDTs; comparisons used light emitting diode (LED) and neon glow tube (NGT) units. All subjects were 18 to 33 years old and were married between January 1 1983 and August 1 1986. The subjects were interviewed by telephone to obtain information on their reproductive and occupational histories and pregnancy risk factors such as smoking and alcohol consumption. All pregnancies occurring between May 1 1983 and December 31 1986 that resulted in a live birth, stillbirth, or spontaneous abortion during the first 28 weeks were recorded. Hours of VDT use were determined from company personnel and payroll records. Ionizing radiation and electromagnetic fields emitted by representative VDTs, LEDs, and NGTs used by the subjects were measured. The effects of VDT use on spontaneous abortions were examined by logistic regression techniques. A total of 882 pregnancies occurred in the cohort and comparisons. The overall crude spontaneous abortion rates among the VDT users and comparisons were 14.8 and 15.9%, respectively. The spontaneous abortion rates among subjects who used VDTs for 0, 1 to 25, or 25+ hours per week were 15.6, 17.2, and 15.4%, respectively. None of the differences were statistically significant. No association between VDT use during the first trimester and spontaneous abortion was found (odds ratio = 0.93). An increased risk was associated with a history of spontaneous abortion, cigarette smoking, and consuming more than eight alcoholic drinks per month during pregnancy. Background ionizing radiation at VDT and nonVDT work sites was similar, ranging from 20 to 400 counts per minute. Subjects who used VDTs had higher abdominal exposures to very low frequency electromagnetic fields. Abdominal exposure to extremely low frequency electromagnetic fields was similar for all subjects. The authors conclude that in the study population no increase in risk for spontaneous abortion associated with occupational VDT use has been found.
NIOSH, Cincinnati, Ohio, 23 pages, 36 references