Time to pregnancy among female greenhouse workers

Abstract

Female greenhouse workers, who constitute a major occupational group exposed to pesticides at childbearing age, were studied to measure the effects of pesticide exposure on time to pregnancy. Data were collected through postal questionnaires with detailed questions on time to pregnancy, lifestyle factors (eg, smoking habits, coffee and alcohol consumption), and worktasks (eg, application of pesticides, re-entry activities, and workhours) of the respondents and their partners in a 6-month period prior to conception of the most recent pregnancy. The relation between time to pregnancy and exposure to pesticides among 398 female greenhouse workers and 524 referents was studied in a Cox's proportional hazards model. The crude fecundability ratio for female greenhouse workers versus the reference group was 1.18 [95% confidence interval (95% CI) 1.03-1.35], but correction for confounding changed the fecundability ratio to 1.11 (95% CI 0.96-1.29). An evaluation of specific biases for time-to-pregnancy studies showed that these results were biased by the reproductively unhealthy worker effect. Restricting the analyses to full-time workers or first pregnancies only resulted in an adjusted fecundability ratio of 0.89 (95% CI 0.67-1.19) and 0.90 (95% CI 0.62-1.32), respectively. Among the primigravidous greenhouse workers, an association was observed between prolonged time to pregnancy and gathering flowers (fecundability ratio 0.46, 95% CI 0.18-1.19). This study may offer some evidence for the hypothesis of adverse effects of pesticide exposure on time to pregnancy, but more research is needed to elucidate these effects.