According to a study published in the New England Journal of Medicine (1999;341:549-555, 601-602), if a woman is pregnant and has hypothyroidism, the IQ of the child may be adversely affected. Women with untreated thyroid deficiency during pregnancy are 4 times more likely to have children with lower IQ scores. 19% of the children whose mothers had undiagnosed hypothyroidism during pregnancy averaged 85 or less on their IQ tests. Children who have an IQ less than 85 are more likely to have difficulties in school. Children between the ages of seven and nine, with mothers who had untreated hypothyroidism, scored an average of seven points lower on IQ tests than children with mothers that had normal thyroid function. The article goes on to say that during the first 12 weeks of pregnancy the fetus relies entirely on the mother for thyroid hormone. They thyroid may play a role in brain development.