Iodine as a component of thyroid hormones is essential for the foetal brain development and iodine is considered by the WHO to be the most important preventable cause of brain damage in the world. It has been shown that even mild iodine deficiency of the mother during pregnancy can lead to lower IQ of the developing child in the UK (Bath et al. 2013). We seek support to explore the database from the AVON Longitudinal Study of Parents and Children (ALSPAC) on the availability of maternal iodine status during pregnancy in healthy young adult participants, who received a brain imaging (magnetic resonance imaging, MRI). We will associate brain anatomical markers such as grey and white matter volume, with the maternal iodine status to test our hypothesis that maternal iodine deficiency during pregnancy has long-term adverse effects on brain development. This study will be pilot study to explore the influence of maternal diet during pregnancy on the offspring’s long-term brain development, cognitive functioning and health.