Too many pregnant women appear to have insufficient intake of iodine, an essential micronutrient needed for normal in utero neurodevelopment and thyroid hormone production.
An estimated 38 million babies born each year in developing countries are at risk of lifelong consequences of brain damage associated with iodine deficiency. But iodine deficiency during pregnancy is not a problem that is only in the developing world, and iodine intake need not be extremely low to have undesirable consequences.
Mitka M. Even Mild Iodine Deficiency During Gestation May Impair Brain Function in Children. JAMA. 2013;309(23):2428. doi:10.1001/jama.2013.7239