The effect of pesticide exposure on time to pregnancy.

The Ontario Farm Family Health Study provided data for examination of the effects of pesticide exposure on time to pregnancy. In this retrospective cohort study of farm couples in Ontario, Canada, the farm operator, husband, and wife completed questionnaires during 1991-1992. We asked about pesticides used on the farm and pesticide activities of the husband and wife for each month of trying to conceive. After exclusions, 2,012 planned pregnancies remained for analysis. We used an analog of the Cox proportional hazards model to calculate conditional fecundability ratios (conditional on pregnancy). There was no strong or consistent pattern of associations of pesticide exposure with time to pregnancy. During exposure intervals in which women participated in pesticide activities (during most of which the men also participated), however, 6 of 13 pesticide exposure categories were associated with a decrease in fecundability (conditional fecundability ratio range = 0.51-0.80). For exposure intervals in which only the men participated in pesticide activities or in which neither men nor women participated in pesticide activities but pesticides had been used on the farm, conditional fecundability ratios ranged from 0.75 to 1.50, with no apparent consistency among pesticide classes, chemical families, or active ingredients.