SWIDDICH is a national ongoing study with multiple sites across Sweden seeking to answer the question “Can iodine substitution improve children’s development?” All participants are randomised into two groups where both will be given a multivitamin tablet, but in one group the tablet also contains 150 µg iodine and in the other control group, the vitamin tablet is without iodine. Every participating family is important as our goal was to recruit approximately 1340 pregnant women.
Our goal is to have healthy and prosperous children and we know that iodine is important for the function of the thyroid gland. Iodine is found in dairy products, fish and seafood, and iodine enriched table salt. Studies have shown that there is no dangerous iodine insufficiency in Sweden today even if iodine intake has decreased in the population during the last few decades. The SWIDDICH study will investigate what importance an iodine substitution during pregnancy has for the children’s health. We will therefore follow the children’s health during their development.
A multivitamin tablet with or without iodine is taken daily until delivery, during which time iodine levels are measured on three occasions. After delivery, we will follow the children with a strong focus on cognitive development. Iodine is important for the brain’s development during fetal life which is why the children will be examined by a psychologist who will evaluate the children’s cognitive ability. The parents will fill in a questionnaire about their child’s behaviour. We are also interested in the children’s iodine levels, thyroid hormones, and related factors. We will also collect information regarding circumstances that can influence the iodine levels with the help of a questionnaire.
Supplementary information regarding the parents/caregivers and the child’s health and living conditions will be collected. Information about the children and the pregnancy will be collected via medical records of hospitals, primary care centres, maternity care centres, child care centres, school health care, and from National Quality Registers (Pregnancy Record Register, Swedish National Neonatal, Child Care and School Care Quality Register), National Board of Health and Welfare (The National Patient Register, The Swedish Prescribed Drugs Register, The Swedish Birth Register) and Statistics Sweden (population registration and facts including education and study results). All collections are approved by the Swedish Ethical Review Authority and no participators will be personally identified in published research results.
If there is heredity thyroid gland diseases, earlier history of thyroid gland disease, other autoimmune diseases or symptoms of thyroid gland disease, normal thyroid function is confirmed via routine blood tests at the Maternity Care Centre.
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Study participants refrain from taking other multivitamins until delivery, with the exception of folic acid and iron.
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