A review of the iodine status of UK pregnant women and its implications for the offspring
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Iodine, as a component of the thyroid hormones, is crucial for brain development and is therefore especially important during pregnancy when the brain is developing most rapidly. While randomised controlled trials of pregnant women in regions of severe iodine deficiency have shown that prenatal iodine deficiency causes impaired cognition, less is known of the effects in regions of mild deficiency. This is relevant to the UK as the World Health Organisation now classifies the UK as mildly iodine deficient, based on a national study of 14–15 year old schoolgirls in 2011. We have previously published a study using samples and data from the UK-based Avon Longitudinal Study of Parents and Children (ALSPAC) that found an association between low iodine status in early pregnancy (urinary iodine-to-creatinine ratio <150 μg/g) and lower verbal IQ and reading scores in the offspring. Though the women in ALSPAC were recruited in the early 1990s, the results of the study are still relevant as their iodine status was similar to that reported in recent studies of UK pregnant women. This review discusses the evidence that mild-to-moderate iodine deficiency during pregnancy has deleterious effects on child neurodevelopment and relates that evidence to the data on iodine status in the UK. It has highlighted a need for nationwide data on iodine status of pregnant women and that a randomised controlled trial of iodine supplementation in pregnant women in a region of mild-to-moderate iodine deficiency with child outcomes as the primary endpoint is required.
KeywordsIodine Nutrition Pregnancy UK Cognition
We are grateful for the advice and help of the co-authors on our own studies (listed in the reference list). We gratefully acknowledge the funding that has supported our studies, including a PhD studentship for SC Bath from Wassen International and the Waterloo Foundation, from The Wellcome Trust for the SPRINT study (Grant No. 083918/Z/07/Z) and from the European Community’s 7th Framework Programme (FP7/2008–2013) Grant Agreement No. 212652 (NUTRIMENTHE “The Effect of Diet on the Mental Performance of Children”). An MRC Population Health Scientist Fellowship (reference MR/K02132X/1) supported S.C. Bath during the writing of this review.
Conflict of interest
Prof. Rayman reported a grant to her institution from Wassen International which helped support Dr. Bath’s Ph.D. studentship; Dr. Bath reported receiving a small honorarium for a lecture from the Dairy Council Northern Ireland and a Ph.D. studentship, partly funded by Wassen International.
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