Greenhouse workers (GW) are exposed to environmental contaminants, including pesticides, that may not only cause known immediate effects such as acute poisoning, but also long-term effects related to chronic exposure to low dosages, a problem that has not been extensively studied This study investigated the relationship between fertility changes and exposure to pesticides in a group of women working in greenhouses.The analysis is based on a retrospective cohort of 145 women working in greenhouses located in the province of Latina, Lazio Region, Italy, who were exposed to pesticides at the time of their first pregnancy. Information on health status, lifestyle, work activity, reproductive history and some confounding factors (age, smoking, alcohol abuse, drug consumption) were collected using a questionnaire. Exposure to pesticides was classified in two levels (high or low) according to the work task and the length of exposure. Changes in fertility were measured in terms of time to pregnancy (TTP), that is the number of non-contraceptive cycles that it takes a couple to conceive. A control group was selected among public administration employees in the same province. The difference in average TTP between exposed and non-exposed groups was analysed by using Student t-test. A Cox proportional hazard model was used to compare TTP between the two groups after correction for confounding factors.In the high-level exposure group average TTP was 10.8 months (+/- 2.0), among the non-exposed average TTP was 6.2 months (+/- 1.0). The difference between exposed and non-exposed was thus 4.6 months (p0.05). Comparison of the distribution of TTP between the high-level exposure group and nonexposed resulted in a hazard ratio of 1.27 (I.C. 95%: 1.03-1.79); the same analysis using the low-level exposure group and non-exposed group yielded a hazard ratio of 1.12 (I.C. 95%: 0.67-1.87).The study showed reduced fertility, in terms of TTP, in the population exposed to pesticides. Among GW, TTP was as much as 50% higher than for the control group. Controlling for confounding factors, the study confirmed an increase in risk for the exposed group. The issue under investigation, however, is complex as health status is not the only factor that needs to be taken into account in studies of reproductive health; emotional status as well as congenital and acquired factors may also have a notable impact on women's fertility. Occupational exposure, therefore, can be said to be a condition requiring careful analysis while bearing in mind that other factors may influence the outcome.