Occupational hazards to fertility and pregnancy outcome.

Occupational reproductive hazards to women have been studied frequently despite the fact that many female reproductive endpoints are not readily observable or routinely recorded in occupational medical records (subfertility, delayed conception, early pregnancy loss, menstrual cycle dysfunction). However, a number of outcomes are fairly readily observable (low birthweight, clinically observed SAB, preterm labor) and medically recorded although they are not generally recorded in the occupational setting. In addition, techniques for observing reproductive outcomes in women are generally less invasive than those in men, particularly with recent developments in urinary monitoring for ovarian function and early pregnancy loss. Although studies of some exposures and outcomes (risk of SAB, low birthweight, or preterm birth with exposure to VDTs or EMFs or exposure to metals and menstrual dysfunction, infertility, or SAB) have shown inconsistent results, a number of findings regarding other associations have been fairly consistent and are very suggestive of causal relationships. Occupational exposure to solvents does appear to increase the risk of dysmenorrhea and SAB, particularly with exposure to organic solvents. Increased risk of adverse reproductive outcomes has also been observed among women working in agricultural settings, but no link has been made to specific exposures. In addition, physical stressors such as shift work, long hours standing, and lifting have been fairly consistently associated with increased risk of SAB or preterm birth. Finally, while complete agreement among studies is lacking, many have observed an increased risk of subfertility or SAB associated with work in medical occupations and with some specific medical exposures, such as nitrous oxide, anesthetic gases and antineoplastic drugs. Much remains to be explored, particularly clarification of the relationship for exposures and outcomes that have shown inconsistent results. These require specific efforts to validate exposures and outcomes, to investigate and control for confounding variables, to consider the effects of multiple comparisons, to study populations of adequate size to provide meaningful statistical analyses, and to make possible the evaluation of dose-response and timing of exposure effects.