Maternal iodine intake, thyroid function in pregnancy and executive function of children at 6 years of age.

Chief Investigator: Dr Shao Jia Zhou

Funding Amount: $74,577

Recipient: University of Adelaide


Iodine is essential for thyroid hormone production and critical for brain development. In pregnancy, inadequate or excessive iodine intake can lead to impaired cognitive function in children, but the level of intake at which impairment occurs is unclear. Recently, pregnant women have increased their iodine intake due to the mandatory iodine fortification and the recommendation for iodine supplementation during pregnancy. We will examine associations between maternal iodine intake, thyroid function in pregnancy and cognitive function of children; and determine iodine levels during pregnancy associated with optimal cognitive function. This work will inform public health policy on iodine supplementation in pregnancy.

Research Outcomes:

Researchers: Dr Shao Jia Zhou, A/Prof Lisa Smithers, A/Prof Rachel Roberts

Research Completed: 2022

Research Findings: Iodine is a nutrient needed for normal growth and it plays a role in the way the brain works and develops. Getting enough iodine in pregnancy is important because the baby’s brain is growing quickly and it relies on iodine supply from the mother’s diet. This study showed that either too little or too much iodine intake in pregnancy may have a negative impact on the brain development of children.

Key Outcomes:

This study is a follow-up of the Pregnancy Iodine and Neurodevelopment in Kids (PINK study) investigating the effect of maternal iodine intake in pregnancy on the neurodevelopmental outcome of children at 18 months of age. Iodine is an essential nutrient which is vital to support the normal growth and development of children. Inadequate iodine intake during a critical period of child development, such as during fetal growth and early childhood, has been linked to poor cognitive function and physical development in children. In the PINK study, we showed that either low or high maternal iodine intake in pregnancy was associated with a lower developmental score in children. It is important to see whether this relationship persists at school age, when cognitive ability is more stable and predictive of lifetime cognition and achievement. The primary aim of the current project is to examine the relationship between maternal iodine intake and executive function of children at 7-8 years of age.

Executive Functions are a set of mental processes that are responsible for the regulation of higher-level cognitive, emotional and behavioural skills. Executive functions develop rapidly in the pre -school period. In this study, executive functions of children were assessed using the Behaviour Rating Inventory of Executive Functions – 2 nd edition (BRIEF 2). Parents and the children’s teachers were asked to complete the BRIEF2 questionnaire as multi-informant assessment provides a better indication of children’s cognitive functioning. Maternal iodine intake in pregnancy, children’s general health, dietary intake and sociodemographic information of the families were also assessed.

Key finding:

• Preliminary analysis indicated that children whose mother’s iodine intake in pregnancy was either low or high were more likely to have an elevated executive function score. Elevated scores indicate more problems with executive functioning.

• The relationship between maternal iodine intake in pregnancy and cognitive function of the children observed in this study is consistent with what was observed when the children were 18 months of age.

• Further in-depth analyses are ongoing to explore sociodemographic factors that influence executive functions of children. • This preliminary finding suggests that either too little or too much iodine intake in pregnancy may have a long-term impact on the cognitive function and behaviour of children. Ensuring appropriate iodine nutrition during the critical period of fetal development is paramount to optimise growth and development of children.

Research Papers: We are in the process of finalising the data analysis and a manuscript is expected to be submitted to a peer-review journal for publication by the end of June 2022. We also plan to present the finding in conferences. The support of CRF will be appropriately acknowledged in any publications, papers, reports or articles resulting from research projects funded by CRF.

Related Publications:

Future Outcomes: No intellectual property was developed during the research project which will be commercialised.

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