Effects of occupational exposure on the reproductive system: core evidence and practical implications.

With the increasing labour force participation among women in Western countries, many women will work during their reproductive years. This will increase the likelihood that women during pregnancy will be exposed to a variety of chemical, physical and psychosocial factors at work. The presence of hazardous conditions in workplaces has raised concerns about their potential effects on pregnancy outcomes and birth defects in offspring. Occupational exposure may directly affect the outcome of pregnancy, such as spontaneous abortion, stillbirth, pre-term birth, small-for-gestational age and birth weight. Occupational exposure may also interact with foetal development, resulting in health effects in the offspring that range from congenital birth defects, neurobehavioral disorders at young age and even cancer in older age. To complicate matters further, occupational exposure among men may result in direct effects on the male reproductive system as well as contribute to negative pregnancy outcomes and birth defects. Thus, the reproductive system of both women and men can be affected by occupational exposure and for most health effects both maternal and paternal exposure may be a relevant route. A timely recognition of the impact of hazardous agents on this broad array of reproductive effects will provide insight into the necessary precautions to be taken for the protection of reproductive health of both women and men. In the scientific literature, there are many publications on adverse reproductive outcomes. Since the reproductive system is a complex, interconnected set of organs, tissues and hormones, there is a large variety of reported adverse effects of environmental agents on the reproductive system. However, the interpretation of an association between an occupational exposure and a reproductive health effect is almost always hampered by the fact that many adverse outcomes may be caused by multiple (work-related) factors, making it extremely difficult to attribute a particular outcome to a specific occupational exposure. In addition, negative outcomes may be due to adverse effects of occupational exposure on both the female and male reproductive system. A third critical issue is that occupational exposure may only be relevant during specific time windows, for example shortly before conception or during early pregnancy. This issue of Occupational Medicine contains three extensive reviews on the epidemiological evidence of occupational hazards to human reproduction. The first comprehensive review focuses on the female reproductive system by addressing the influence of maternal exposure on fertility and pregnancy outcomes [1]. In the second review, the focus is the impact of maternal exposure on the adverse effects in the offspring, as characterized by a variety of birth defects [2]. The third review shifts emphasis towards the contribution of occupational exposure among men to male reproductive dysfunction, primarily measured by semen quality and fecundity [3]. Together these reviews present a comprehensive picture of the role of occupational risk factors in reproductive health. The main aims of this accompanying article are to present a summary of the core findings in the three reviews, to discuss important constraints in the interpretation of these results and then derive practical implications for research and practice in occupational health.