Identifying environmental risk to male reproductive function by occupational sperm studies: logistics and design options.

Malfunction of the male reproductive system might be a sensitive marker of environmental hazards, the effects of which may extend beyond reproductive function. The testis is more vulnerable to heat and ionising radiation than any other organ of the body and several xenobiotics are known to disrupt spermatogenesis after low level exposure. Studies of environmental impact on human health are often most informative and accurate when carried out in the workplace where exposures can be high and easy to document. Semen analysis provides readily obtainable information on testicular function. The main advantages in comparison with functional measures such as fertility rates and time taken to conceive are the possibilities to examine men independently of marriage and pregnancy, to find changes of fecundity with different exposures within the same person and to detect adverse effects when no alteration of fertility is yet taking place. In the implementation of an occupational sperm study considerable attention must be paid to logistic issues. A mobile laboratory unit for initial semen preparation and processing may in some situations increase worker compliance and the quality of sperm cell motility. The cross sectional design which has been used in almost all male reproductive studies so far has several severe limitations including selection bias because of differential participation, difficulties in defining a suitable reference group, and lack of information about the time dimension of the cause-effect relation. The longitudinal design deals adequately with most of these constraints. Semen samples are collected before, during, and possibly after exposure to the risk factor of interest and causal inferences are based upon change of semen variables within a man over time rather than upon differences between men. The logistics of the longitudinal study may benefit from pre-employment health examinations to enrol newly hired workers and require fewer participants to obtain comparable statistical power. In conclusion, andrological methods and epidemiological designs are available for the implementation of valid studies concerned with environmental impact on human testicular function. Occupational sperm studies should probably not be the first choice when the objective is initial screening of environmental impact on fertility but should be implemented when their is a need to corroborate or refuse earlier evidence that specific exposures have impact on testicular function

Maternal occupation during pregnancy, birth weight, and length of gestation: Combined analysis of 13 European birth cohorts

Objectives We assessed whether maternal employment during pregnancy – overall and in selected occupational sectors – is associated with birth weight, small for gestational age (SGA), term low birth weight (LBW), length of gestation, and preterm delivery in a population-based birth cohort design. Methods We used data from >200 000 mother-child pairs enrolled in 13 European birth cohorts and compared employed versus non-employed women. Among employees, we defined groups of occupations representing the main sectors of employment for women where potential reproductive hazards are considered to be present. The comparison group comprised all other employed women not included in the occupational sector being assessed. We performed meta-analyses of cohort-specific estimates and explored heterogeneity. Results Employees had a lower risk of preterm delivery than non-employees [adjusted odds ratio (ORadj) 0.86, 95% confidence interval (95% CI) 0.81–0.91]. Working in most of the occupational sectors studied was not associated with adverse birth outcomes. Being employed as a nurse was associated with lower risk SGA infants (ORadj 0.91, 95% CI 0.84–0.99) whereas food industry workers had an increased risk of preterm delivery (ORadj 1.50, 95% CI 1.12–2.02). There was little evidence for heterogeneity between cohorts. Conclusions This study suggests that, overall, employment during pregnancy is associated with a reduction in the risk of preterm birth and that work in certain occupations may affect pregnancy outcomes. This exploratory study provides an important platform on which to base further prospective studies focused on the potential consequences of maternal occupational exposures during pregnancy on child development

Pregnancy: occupational aspects of management: concise guidance

Most pregnant women are exposed to some physical activity at work. This Concise Guidance is aimed at doctors advising healthy women with uncomplicated singleton pregnancies about the risks arising from five common workplace exposures (prolonged working hours, shift work, lifting, standing and heavy physical workload). The adverse outcomes considered are: miscarriage, preterm delivery, small for gestational age, low birth weight, pre-eclampsia and gestational hypertension. Systematic review of the literature indicates that these exposures are unlikely to carry much of an increased risk for any of the outcomes, since small apparent effects might be explicable in terms of chance, bias, or confounding, while larger and better studies yield lower estimated risks compared with smaller and weaker studies. In general, patients can be reassured that such work is associated with little, if any, adverse effect on pregnancy. Moreover, moderate physical exercise is thought to be healthy in pregnancy and most pregnant women undertake some physical work at home. The guidelines provide risk estimates and advice on counselling

Identifying environmental risk to male reproductive function by occupational sperm studies : logistics and design options

Contains fulltext : 24070___.PDF (publisher's version ) (Open Access)Co-authored by the Asclepios group, to which belong G.A. Zielhuis and H.J.T.M. Thui

Miscarriage and occupational activity: a systematic review and meta-analysis regarding shift work, working hours, lifting, standing and physical workload

OBJECTIVE: Previous studies have indicated that shift work, long working hours, and prevalent workplace exposures such as lifting, standing, and physical workload increase the risk of miscarriage, but the evidence is conflicting. We conducted a systematic review of original research reports.METHODS: A search in Medline and EMBASE 1966-2012 identified 30 primary papers reporting the relative risk (RR) of miscarriage according to ?1 of 5 occupational activities of interest. Following an assessment of completeness of reporting, confounding, and bias, each risk estimate was characterized as more or less likely to be biased. Studies with equivalent measures of exposure were pooled to obtain a weighted common risk estimate. Sensitivity analyses excluded studies most likely to be biased.RESULTS: Working fixed nights was associated with a moderately increased risk of miscarriage (pooled RR 1.51 [95% confidence interval (95% CI) 1.27-1.78, N=5), while working in 3-shift schedules, working for 40-52 hours weekly, lifting >100 kg/day, standing >6-8 hours/day and physical workload were associated with small risk increments, with the pooled RR ranging from 1.12 (3-shift schedule, N=7) to 1.36 (working hours, N=10). RR for working hours and standing became smaller when analyses were restricted to higher quality studies.CONCLUSIONS: These largely reassuring findings do not provide a strong case for mandatory restrictions in relation to shift work, long working hours, occupational lifting, standing, and physical workload. Considering the limited evidence base, however, it may be prudent to advise women against work entailing high levels of these exposures and women with at-risk pregnancies should receive tailored individual counseling