title: Occupational exposure to chemical substances and time to pregnancy: a systematic review.
abstract: BACKGROUND
  Fertility problems are an important health issue, as 10-15% of couples have difficulties conceiving. Reproductive function is thought to be compromised by lifestyle behaviours, but environmental contaminants and work-related factors are also thought to play a role. The objective of this review was to systematically summarize the available evidence concerning the influence of occupational exposure to chemicals on time to pregnancy (TTP).
  
  
  METHODS
  A structured search on occupational exposure to chemicals and TTP was carried out in PubMed and Embase. Studies were included if TTP was used as outcome measure and exposure to chemicals at the job level was described. In total, 49 studies were included in this review.
  
  
  RESULTS
  Studies varied widely in characterization of exposure, hampering a meta-analytic approach across all studies. For lead, strong indications for adverse effects on TTP were present, supporting the mandatory provisions for pregnant women being exposed to lead in many countries. These indications were also found for pesticide exposure, and one could argue that couples working in agriculture or horticultural trades must be informed about the risks of pesticide exposure. Epidemiologic evidence on other chemicals, such as organic solvents, and other metals remains equivocal, hampering clear counselling of couples who are trying to become pregnant.
  
  
  CONCLUSIONS
  Despite some uncertainties in the evidence base, it may still be prudent to advise against lead and pesticide exposure at the workplace for couples trying to conceive. This review also identifies several priorities for future studies in the field of occupational epidemiology.
authors.affiliation: Department of Public Health, Erasmus Medical Centre, 3000 CA Rotterdam, The Netherlands.
authors.forename: Claudia A
authors.initials: CA
authors.lastname: Snijder
authors.forename: Egbert
authors.initials: E
authors.lastname: te Velde
authors.forename: Nel
authors.initials: N
authors.lastname: Roeleveld
authors.forename: Alex
authors.initials: A
authors.lastname: Burdorf
mesh_terms: D000383:Agriculture; D005260:Female; D005306:Fertilization; D006801:Humans; D007854:Lead / Q000633:toxicity*; D008297:Male; D018811:Maternal Exposure / Q000009:adverse effects; D008670:Metals / Q000633:toxicity; D016273:Occupational Exposure / Q000009:adverse effects*; D018812:Paternal Exposure / Q000009:adverse effects; D010575:Pesticides / Q000633:toxicity*; D011247:Pregnancy; D012997:Solvents / Q000633:toxicity*; D061685:Time-to-Pregnancy / Q000187:drug effects*
chemical_list: D008670:Metals; D010575:Pesticides; D012997:Solvents; D007854:Lead