Iodine deficiency during pregnancy
impairs the neurological development of the fetus. In
areas of severe chronic iodine deficiency, maternal
and fetal hypothyroxinemia can occur from early
gestation onwards.7 Thyroid hormone is required
for normal neuronal migration and myelination of
the brain during fetal and early postnatal life, and
hypothyroxinemia during these critical periods causes
irreversible brain damage, with mental retardation
and neurological abnormalities.7 The consequences
depend upon the timing and severity of the hypothyroxinemia
(Table 3).