Recruitment in the SWIDDICH study concluded in May 2025 with 1337 included participants, and 1537 when including the pilot study. Thus, we have reached the target specified in the power calculations, enabling us to investigate the effect on child neurodevelopment.
SWIDDICH is a national study with multiple sites across Sweden seeking to answer the question “Can iodine substitution improve children’s development?”
Participants are randomised into two groups where both will be given a multivitamin tablet, but in one group the tablet also contains 150µg iodine and in the other control group, the vitamin tablet is without iodine.
The iodine supplementation is given to pregnant women based on the hypothesis that it will enhance the neurological development of their children up to preschool or school age. With participant recruitment now complete, only follow-up of the children up to 7 years of age remains before it is possible to address the primary research question. However, earlier insights will be gained from secondary outcomes, such as the effects of iodine supplementation on maternal iodine deficiency risk and delivery-related complications.
The study protocol was published in 2018;
Manousou S, Johansson B, Chmielewska A, Eriksson J, Gutefeldt K, Tornhage CJ, Eggertsen R, Malmgren H, Hulthen L, Domellöf M, Nystrom Filipsson H. Role of iodine-containing multivitamins during pregnancy for children’s brain function: protocol of an ongoing randomised controlled trial: the SWIDDICH study. BMJ Open. 2018 Apr 10;8(4):e019945. doi: 10.1136/bmjopen-2017-019945.
“This is an important milestone and a huge achievement – it has taken us 8 years to complete recruitment” said Prof Magnus Domellöf, research lead for the study at the Umeå site.
More information on the study can be found on its dedicated website: https://swiddich.se/en/about-the-study/