The Problem Iodine Deficiency: Iodine deficiency is the leading preventable cause of intellectual and developmental disabilities in the world. Iodine is a crucial nutrient for healthy brain development. When populations are deficient, pregnant women and newborns are particularly affected. Iodine deficiency can lead to cognitive and developmental impairment, as well as miscarriage, stillbirth, and infant mortality. Today, tens of millions of people remain at risk of iodine deficiency, according to estimates from the World Health Organization, UNICEF, and IGN.