Organophosphate Urinary Metabolite Levels during Pregnancy, Delivery and Postpartum in Women Living in Agricultural Areas in Thailand: Pornpimol KONGTIP, et al. Department of Occupational Health and Safety, Faculty of Public Health, Mahidol University, Thailand—Objective: Prenatal exposure to organophosphate pesticides can lead to developmental neurotoxicity. A longitudinal birth cohort was established to investigate pesticide exposures from different agricultural activities. Maternal urinary organophosphate metabolites were measured at 28 weeks of pregnancy (n=86), delivery (n=67) and 2 months postpartum (n=51). Method: Subjects were interviewed with questionnaires about work, home and behavioral factors potentially associated with pesticide exposures, and spot urine samples were also collected. The urine samples were analyzed for dimethyl phosphate (DMP), diethyl phosphate (DEP), diethyl thiophosphate (DETP) and diethyl dithiophosphate (DEDTP), using gas chromatography-mass spectrometry.