Iodine is essential for thyroid hormone synthesis. We have known for a long time that severe iodine deficiency during pregnancy may affect the cognitive development of the unborn child. According to a recent Lancet study, even children born to women with mild-to-moderate iodine deficiency during pregnancy are at increased risk for lower IQ and reading ability (assessed at age 9). The most severe effects were observed among children born to women with severe deficiency (<50 mcg/g iodine:creatinine ratio).
In the United States and Canada, where the use of iodized table salt is common, rates of iodine deficiency are low. However, iodine deficiency is becoming more common in some developed countries, including the United Kingdom. Women who do not consume dairy products (especially as part of vegan diet) or iodized salt are at greater risk for iodine deficiency. The American Thyroid Association recommends that women from the US receive a supplement of 150 mcg of iodine (in the form of potassium iodide) daily during pregnancy and lactation, which is the dose included in the majority of prenatal vitamins marketed in the United States.
Ruta Nonacs, MD PhD
Bath SC, Steer CD, Golding J, et al. Effect of inadequate iodine status in UK pregnant women on cognitive outcomes in their children: results from the Avon Longitudinal Study of Parents and Children (ALSPAC). Lancet 2013.
Zimmerman MB. Iodine Deficiency. Endocrine Reviews 2009; 30 (4): 376.
Iodine Key for IQ; Pregnancy Deficiency Affects Kids’ Brains (Medscape)