Some evidence suggests that early exposure to high levels of fluoride may have a negative impact on the cognitive outcomes in children. Given the conflicting findings from previous studies, further research is necessary to understand the effect of fluoride on cognitive development. Our aim is to assess the association of exposure to fluoride during early pregnancy and childhood with offspring cognitive development. We will study mother-child pairs from the Avon Longitudinal Study of Parents and Children (ALSPAC) to address the aim of our study. We will estimate fluoride exposure from diet and dental products using the food frequency and oral hygiene questionnaires collected from mothers during pregnancy and from their children when 6, 15 and 24 months old. We will then investigate the link between fluoride exposure and the cognitive outcomes of offspring which were measured at 18 months of age during ALSPAC clinical assessments.