A small amount of mercury vapor is released from dental amalgam restorations during mastication. This mercury can potentially influence pregnancy outcomes. The long-term goal of this study is to determine whether restorations increase the risk that a pregnancy will end with a spontaneous abortion, stillbirth, low birth weight infant, or congenital abnormality. A pilot study will make use of dental and medical records available at a health care center in Prague, Czechoslovakia. The gynecological records of an estimated 2441 Czech women who were pregnant during the 14-month period from 11/01/90 to 12/31/91 will be screened. An estimated 414 women whose pregnancies ended with 1) spontaneous abortions or stillbirths (307), 2) low birth weight infants (75), or 3) congenital abnormalities (32) will be selected as cases for a case-control (retrospective) study. An equal number of controls will be randomly selected from all pregnancies that resulted in live births during the same period. Data for both cases and controls will be transferred from the gynecological, obstetric, family practice, and dental records to a computer database. The data will be analyzed using a logistic regression to determine whether the exposure variable, e.g., whether the subject has a large, medium, or small exposure to amalgam restorations, effects the relative risk of adverse pregnancy outcome. Separate analyses will be performed for two dependent variables: 1) the spontaneous abortion or stillbirth case-control status and 2) the low birth weight infant case-control status. Because of the limited number of cases, the congenital abnormality data will be tabulated but not analyzed. The regressions will estimate adjusted relative risks (odds ratios) corrected for potential confounding variables such as age, alcohol consumption, or previous stillbirths. This pilot study is capable of detecting fairly large relative risks. It will demonstrate the feasibility of a study capable of detecting smaller relative risks.
