Pregnancy outcome among women exposed to pesticides through work or residence in an agricultural area.

The study population consisted of women enrolled in a southern California community clinic perinatal program. All women entering the program between January 1987 and December 1989 were asked to participate, and a cohort of 535 women was included in the study. Primarily Hispanic, of low income and educational level, many had recently immigrated from Mexico. They were potentially exposed to pesticides and other agricultural chemicals occupationally and/or environmentally because agricultural production in San Diego County is among the highest in the state. Study methods consisted of biologic assay of maternal blood samples for determination of cholinesterase activity and concurrent patient interviews to determine exposure history by self report. These assessments were conducted on each participant approximately once each trimester. Self-report and blood assay data were analyzed using chi 2, the Mantel-Haenszel extension of chi 2, and risk ratios to determine the association between pesticide exposure and spontaneous abortion, preterm birth, low birth weight and toxemia. No difference between exposed and unexposed women was noted for risk of preterm birth or toxemia. Subjects who experienced spontaneous abortion were all unexposed, and the rate of spontaneous abortion was 2.1%, less than generally expected. A greater incidence of low birth weight among unexposed women indicates that exposure may have had a "protective" effect.