American Journal of Industrial Medicine 15: 357-358 (1989)

LETTER TO THE EDITOR

The Risk of Miscarriage and Birth Defects Among Women Who Use Visual Display Terminals During Pregnancy

On the surface, the article, “The Risk of Miscarriage and Birth Defects Among Women Who Use Visual Display Terminals During Pregnancy,” [Goldhaber, et al., 19881 seems to contribute substantial new information to the ongoing debate over the health effects of visual display terminal (VDT) use on women. Publication comes at a time of increasing sensitivity to the issue and growing calls for regulations surrounding the use of VDTs. An example of this is the recent legislation in Suffolk county in New York. In this environment, the publication of an article finding an elevated miscarriage risk in pregnant women, a finding at variance with previous studies, is certain to increase the pressures for regulatory action if allowed to go unchallenged. It goes without saying that any medical study should be able to withstand the searchlight of scientific enquiry, in particular, to establish that no hidden factors or biases were present that could have influenced the findings. The authors themselves must have been mindful of this when they concluded that there was a need for further investigations with large cohort studies of working women. They are right, but, unfortunately, the planning, funding and implementation of such a trial may take years, and in the meantime the clamour for control will increase immediately, fueled in part by this study irrespective of the merits of the findings.

Problems with the results of the study that the authors themselves suggested or identified were as follows:

1 . The only dose-response relationship identified was with administrative support/ clerical workers;

2. Working women with no VDT exposure had 1.2 times the miscarriage risk of nonworking women in the reference group;

3. Elevated risks with high VDT use occurred in all occupations relative to non- working women, but the influence of VDTs was unclear in three out of four occupations. Technical support/sales workers had elevated relative risks for all levels of VDT use including the “none” category for workers who did not use VDTs, suggesting an occupational effect not related to VDTs;

4. Managers/professionaIs had an unusually low risk with moderate VDT use; 5 . Women with miscarriages may have overreported their exposures to VDTs, and/or

women with normal births may have underreported theirs; 6. The numbers of high-use VDT workers were too small to draw reliable conclusions

for all occupations with the exception of administrative support/clerical workers.

Address correspondence to Dr. Harry Robinson, Director Medical Epidemiology, New York Telephone. Room 2561, 1095 Avenue of the Americas, New York, NY 10036. Accepted for publication July 7 , 1988.

0 1989 Alan R. Liss, Inc.

358 Robinson

The subjects in this study were part of a larger cohort of pregnant women identified during a nearly 1-year period that the pesticide malathion was sprayed in the San Francisco Bay area of California. The objective of the larger study was to study the effects of the spraying and other environmental exposures such as VDTs. The only information provided on the effects of these exposures was that self-reported exposures to pesticides were not elevated among women who reported problem pregnancies (miscarriages and/or birth defects?). However, the reader is left to speculate if any correlations were found between VDT usage, malathion exposure, and miscarriages.

It is well known that genetic incompatibilities between parents can result in the mothers suffering an excessive number of miscarriages irrespective of occupational exposures. In adjusting their odds ratios (Table III), the authors used “previous miscarriage” or “birth defect” as a dichotomy (yesho). This was unfortunate since no significant associations with birth defects existed for VDT exposure level. The effect of the merge of the two outcomes would therefore constitute a dilution of any adjustment effects of previous miscarriages. The variable, previous miscarriages, should have been expressed as a proportion of miscarriages to total births and used as an independent adjustment factor.

The comments of the authors relating to the possibility of erroneous reporting of VDT exposure by the women raises interesting questions regarding forces that may have influenced their responses. It is well known that major advocates of regulation for VDTs are unions, and if some of the subjects are union members, it might be revealing to tabulate the membership proportions by level of VDT exposure. If this information is not available, an attempt should be made to at least ascertain if some of the women using VDT belong to unions. This would either eliminate or confirm the existerice of a possible major source of response bias.

The major concern of all contributors to the debate over the use of VDTs is, or should be, the health of the persons who use them. If there are deleterious effects, then measures need to be taken to eliminate or ameliorate them, and, in fact, many companies have addressed ergonomic factors to improve worker well-being and productivity. By the same token, before adding a further layer of regulation to industry, it behooves all of us in the medical field to have a reasonable certainty that such regulation is necessary. Failure to do so will not improve the health of VDT workers and has the potential to create severe administrative and economic problems for the companies that employ them.

The Goldhaber article does not provide information of sufficient clarity to permit conclusions surrounding the use of VDTs by women during their pregnancies.

Harry Robinson, ScD, Director, Medical Epidemiology,

New York Telephone, New York, NY 10036

REFERENCES

Goldhaber MK, Polen MR, Hiatt RA (1988): The risk of miscarriage and birth defects among women who use visual display terminals during pregnancy. Am J Ind Med 13695-706.