Birth defects and exposure to video display terminals during pregnancy. A Finnish case-referent study

In a test of the widely publicized allegation that exposure to video display terminals causes birth defects, interview forms of mothers of 1 475 children reported consecutively to the Finnish Register of Congenital Malformations to have defects of the central nervous system, orofacial clefts, skeletal defects, or cardiovascular malformations and the forms of the same number of their paired referents were studied. The scrutiny revealed 490 mothers with occupational titles indicating potential exposure to video display terminals. Of the 490, 235 were case mothers and 255 were referents. Then, unaware of the case-referent status, three members of the research team perused the mothers' interview descriptions of workday activities for information indicating exposure to video display terminals. Work with such terminals during the first trimester of pregnancy was ascertained for 111 mothers. Of these, 51 were case mothers and 60 were referents. The comparison of the mothers exposed to video display terminals during the first trimester with those not exposed at all showed a crude odds-ratio point estimate of 0.9 with 95% confidence limits of 0.6 and 1.2. Adjustment for potential confounders by multivariate logistic regression methods did not materially affect the risk estimates. The results did not indicate a teratogenic risk for operators of video display terminals.