Around 40% of pregnant women in the UK may not have enough iodine in their bodies to meet World Health Organization definitions of sufficiency. This matters because iodine is essential for foetal brain development, and even mild-to-moderate deficiencies—whose effects are poorly understood—could harm pregnancy outcomes and a child’s later cognitive and motor skills. The researchers will measure iodine levels in thousands of stored urine samples from the Born in Bradford birth cohort, then link those levels to detailed health records for mothers and children, including birthweight, gestational diabetes, and childhood literacy and numeracy. They will also track 300 women across all three trimesters and after birth to see how iodine status changes, and compare results with a more nationally representative sample. If the research succeeds, it could provide the first robust evidence on whether mild-to-moderate iodine deficiency in British pregnancy is a hidden public health problem, and inform clear dietary guidance for expectant mothers.
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Background: Pregnant women may be particularly vulnerable to iodine deficiency as requirements increase to support foetal development. There is limited information concerning how maternal iodine status changes during pregnancy. Severe iodine deficiency is associated with deleterious health outcomes during pregnancy including gestational diabetes, preeclampsia, stillbirth, and increased mortality. For the foetus, severe iodine deficiency results in reduced birthweight, increased mortality and neurodevelopmental issues. Several studies suggest 40% of pregnant mothers in the UK may not meet the WHO definition of iodine sufficiency. Although the effects of severe iodine deficiency are known, the impact of mild-to-moderate deficiencies on maternal health and associated foetal and childhood development are not well understood. Aims: 1) To provide up-to-date information on iodine status in pregnant women in the UK, including changes during pregnancy and lactation, and the role of diet. 2) To quantify any associations between iodine status during pregnancy, pregnancy outcomes, and cognitive and motor development of the child. 3) To compare the iodine status of mothers in the Born in Bradford cohort to a more nationally representative sample. Research plan and methods: We will utilize the Born in Bradford (BiB) birth cohort which recruited over 12000 pregnant women between 2007- 2009, and has biobanked 6971 spot urine samples collected at 26-28 weeks gestation. Data are available on health outcomes during pregnancy including gestational diabetes, preeclampsia, blood pressure, length of gestation, mortality, mental health. Child outcome measures at birth include weight, length, head circumference, small-for-gestational-age. Childhood developmental measures include height, weight, growth trajectories, motor skills, literacy, numeracy and mental health. We will measure all maternal urine samples in BiB to allow sufficient power to detect potential modest-sized associations. This will be conducted using inductively coupled plasma mass spectrometry (ICPMS). All maternal baseline characteristics and associated outcome data are available for extraction from the primary BiB database. We will apply multiple logistic regression and multiple linear regression to ascertain potential associations between maternal iodine status and health and developmental outcomes. Cubic splines will be used to model any nonlinear dose-response associations, making no assumptions regarding any predefined thresholds. We will also conduct a longitudinal substudy to ascertain how iodine status varies between trimesters. 300 pregnant women will be recruited at 12 week dating scans and the following collected: baseline characteristics, urine samples for iodide analysis, blood for thyroid stimulating hormone (TSH), free thyroxine (fT4) and triodothyronine (fT3), Glomerular Filtration Rate (GFR) based on serum creatinine, visual inspection of the thyroid using standard methods, dietary intake using a 24h recall tool (myfood24). Data collection will be repeated at 26 and 36 weeks gestation, and 6, 18 and 30 weeks postpartum. The proposed substudy will clarify how iodine status alters in pregnancy and lactation, and any associated thyroid hormone changes. We will identify key sources of iodine in the diet and ascertain dietary patterns associated with different iodine status. To compare results to a more nationally representative sample, spot urines will be analysed from approximately 650 women in the SCOPE birth-cohort (London, Leeds and Manchester). Research team: The research team comprises a molecular epidemiologist (Hardie) with extensive experience of nutritional biomarkers, a biostatistician with expertise in birth cohorts, child health and nutrition (Greenwood), the BiB study lead (Wright), nutritional epidemiologist (Cade), and obstetrician (Simpson) and endocrinologist (Stewart). The team will be supported by four external expert advisors (Zimmermann, Alw
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