In April 2020 researchers from the UK published their review of the medical scientific literature to assess the effect of iodine supplementation in mildly-to-moderately deficient pregnant women on maternal and infant thyroid function and child cognition. Mild-to-moderate iodine deficiency was defined as a urinary iodine level of 50-149 µg/L. A total of 37 studies met the search criteria and were included in the review. Results showed that in most studies iodine supplementation had no effect on maternal or infant thyroid-stimulating hormone and free thyroxine. Most studies found that iodine supplementation reduced maternal thyroglobulin and in 3 studies it prevented or diminished an increase in maternal thyroid volume during pregnancy. Only 3 studies assessed child neurodevelopment and of these two showed that iodine supplementation had no effect on child cognitive, language or motor scores. The researchers therefore concluded that there was currently insufficient good-quality evidence to support a recommendation for iodine supplementation in mildly-to-moderately deficient pregnant women. Further well-designed studies, with child cognitive outcomes, are required.
Dineva M et al. Systematic review and meta-analysis of the effects of iodine supplementation on thyroid function and child neurodevelopment in mildly-to-moderately iodine-deficient pregnant women. Am J Clin Nutr. 2020 Apr 22. [Epub ahead of print]