Studies that suggested that exposure to OP pesticides during pregnancy was associated with symptoms of pervasive developmental disorder (PDD) in toddlers [23, 24] and to autism spectrum disorder (ASD) traits in children [5] raised the question of whether infants born to women with low PON1 status were more susceptible to the detrimental effect of OP exposure during pregnancy. This evidence concerns the gene PON1 and autism spectrum disorder.