Prenatal Iodine Supplementation and Early Childhood Neurodevelopment

A randomized controlled trial to determine the effect of reducing iodine from vitamin and mineral supplements for pregnant women who have adequate iodine intakes (\>165 μg/d from food alone) on cognitive development of children at 24 months of age.

It is known that severe iodine deficiency during pregnancy leads to profound intellectual disabilities in the child. Following results of a 2004 national survey of school-aged children showing that mild iodine deficiency had re-emerged in the south-eastern parts of Australia, the Australian government mandated the addition of iodine to salt used in bread making to increase population iodine intake. It is also recommended that all pregnant and lactating women take an additional iodine supplement containing 150 µg/d of iodine. Since this time, further evidence has emerged from cohort studies that children born to women with high iodine intake (as well as low iodine intake) have poorer neurodevelopmental scores, suggesting that more tailored supplementation may be a better strategy. Our PoppiE trial will determine if limiting iodine supplementation in women who already consume adequate iodine from food, improves cognitive scores in early childhood. A total of 754 pregnant women from around Australia who are ≤13 weeks of gestation will be enrolled and randomised to receive a standard prenatal vitamin and mineral supplement with a reduced amount of iodine (20 μg - intervention) or a standard prenatal vitamin and mineral supplement with 200 μg of iodine (control). The control supplement contains a level of iodine to match the amount in most commonly used vitamin and mineral supplements sold in Australia. Infant neurodevelopment at 24 months of age will be assessed using the Bayley-IV and conducted at participating centres or a location convenient to the family.

Inclusion Criteria: * Pregnant women ≤13 weeks of gestation. * Consume greater than 165 µg/d of iodine from food alone based on our validated Iodine Specific Food Frequency Questionnaire (I-FFQ). * English is main language spoken at home as child will need to understand and take instruction in English to participate in the neurodevelopmental assessment. * Able to give informed consent. Exclusion Criteria: * Known history of thyroid disease. * Previous child diagnosed with thyroid dysfunction. * Carrying a fetus with a known or suspected congenital abnormality.