Association between in utero organophosphate pesticide exposure and abnormal reflexes in neonates

The detrimental effects of organophosphate pesticide (OP) exposure on neurodevelopment have been shown in animals. The present study aimed to assess the relationship between in utero and early postnatal OP exposure and neonatal neurobehavior in humans, as measured by seven clusters (habituation, orientation, motor performance, range of state, regulation of state, autonomic stability, and reflex) on the Brazelton Neonatal Behavioral Assessment Scale (BNBAS). We assessed 381 infants < or = 2 months old and born to women participating in the Center for the Health Assessment of Mothers and Children of Salinas (CHAMACOS) study, a longitudinal, birth cohort study of low-income, Latina women living in the agricultural community of the Salinas Valley, California. Exposure to OP pesticides was determined by urinary levels of dialkylphosphate (DAP) metabolites, including dimethyl and diethylphosphate metabolites, measured twice during pregnancy (M = 14 and 26 weeks gestation) and once post-delivery (M = 7 days postpartum). The relationship between exposure and BNBAS performance was examined for the entire sample and stratified by the median age at assessment, 3 days. We observed a significant association between exposure and the reflex cluster for the entire sample and for infants >3 days old (n = 184). Among the >3 day old infants, increasing average prenatal urinary metabolite levels were associated with both an increase in number of abnormal reflexes (total DAP: adjusted beta = 0.53, 95% CI = 0.23, 0.82; dimethyls: adjusted beta = 0.41, 95% CI = 0.12, 0.69; diethyls: adjusted beta = 0.37, 95% CI = 0.09, 0.64), and the proportion of infants with more than three abnormal reflexes (total DAP: adjusted OR = 4.9, 95% CI = 1.5, 16.1; dimethyls: adjusted OR = 3.2, 95% CI = 1.1, 9.8; diethyls: adjusted OR = 3.4, 95% CI = 1.2, 9.9). No detrimental associations were found between postnatal urinary metabolite levels and any of the BNBAS clusters for infants < or = 3 or >3 days old at assessment. Whether neonatal reflex functioning is predictive of neuropsychological functioning as the child matures will continue to be evaluated in this birth cohort.