For pregnant women with mild iodine deficiency, taking a 200 μg iodine supplement daily does not improve their child's thinking or movement skills by age 5.7, and may be linked to slightly lower motor skills at age 2, suggesting no overall advantage for brain development.

Not getting enough iodine when kids are growing can hurt their brain development for good, because iodine is needed to make important brain hormones.

Taking standard iodine supplements during pregnancy can raise iodine levels in urine beyond the safety threshold recommended by the WHO, even in women who are only mildly deficient.