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Nutrition during the early life cycle

Iodine status of pregnant women with obesity from inner city populations in the United Kingdom



Iodine is essential for foetal neurodevelopment and growth. Requirements increase in pregnancy to support increased thyroid hormone synthesis for maternal and foetal requirements, and for foetal transfer. Iodine deficiency in pregnancy is widely reported, and obesity has been associated with sub-optimal thyroid function. We evaluated iodine status and its relation with birthweight in a secondary analysis of pregnant women with obesity from multi-ethnic inner-city settings who participated in the UK Pregnancies Better Eating and Activity trial (UPBEAT).


Iodine and creatinine concentrations were evaluated in spot urine samples in the second (15+0–18+6 weeks, n = 954) trimester of pregnancy. We assessed iodine status as urinary iodine concentration (UIC) and urinary iodine-to-creatinine ratio (UI/Cr) and applied WHO/UNICEF/IGN population threshold of median UIC > 150 µg/L for iodine sufficiency. Relationships between iodine status and birthweight were determined using linear and logistic regression with appropriate adjustment, including for maternal BMI and gestational age.


Median (IQR) UIC and UI/Cr in the second trimester of pregnancy were 147 µg/L (99–257) and 97 µg/g (59–165), respectively. An UI/Cr <150 μg/g was observed in 70% of women. Compared to women with UI/Cr >150 µg/g, there was a trend for women with UI/Cr <150 µg/g to deliver infants with a lower birthweight (β = −60.0 g; 95% CI −120.9 to −1.01, P = 0.05).


Iodine status of pregnant women with obesity from this cohort of UK women was suboptimal. Lower iodine status was associated with lower birthweight.

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JF was supported by the Medical Research Council (grant number MR/R019177/1). KVD is supported by the British Heart Foundation FS/17/71/32953. SLW, LP and ACF are supported by Tommy’s charity. LP is supported by the Biomedical Research Centre at Guy’s and St Thomas’ NHS Foundation Trust and Kings College London. KMG is supported by the UK Medical Research Council (MC_UU_12011/4), the National Institute for Health Research (NIHR Senior Investigator (NF-SI-0515-10042), NIHR Southampton 1000DaysPlus Global Nutrition Research Group (17/63/154) and NIHR Southampton Biomedical Research Centre (IS-BRC-1215-20004)), the European Union (Erasmus + Programme Early Nutrition eAcademy Southeast Asia-573651-EPP-1-2016-1-DE-EPPKA2-CBHE-JP and ImpENSA 598488-EPP-1-2018-1-DE-EPPKA2-CBHE-JP), British Heart Foundation (RG/15/17/3174) and the US National Institute On Aging of the National Institutes of Health (Award No. U24AG047867).

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ACF and JF conceived of the study. ACF, JF, CG and AB designed the study. KVD and ACF analysed the data. JF, KVD, SLW and ACF interpreted the data. JF, KVD and ACF wrote the manuscript. LP, JHL, KMG contributed to data interpretation and provided feedback on the manuscript. All authors have read and approved the final manuscript.

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Correspondence to Jessica Farebrother.

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Conflict of interest

KMG has received reimbursement for speaking at conferences sponsored by companies selling nutritional products, and is part of an academic consortium that has received research funding from Abbott Nutrition, Nestec, BenevolentAI Bio Ltd. and Danone. The other authors report no potential conflicts of interest.

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Farebrother, J., Dalrymple, K.V., White, S.L. et al. Iodine status of pregnant women with obesity from inner city populations in the United Kingdom. Eur J Clin Nutr 75, 801–808 (2021).

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