Pregnant women with untreated hypothyroidism (low thyroid) deliver babies with mild mental retardation, but experts do not agree that this justifies routine screening of pregnant women, according to a new study. The study was conducted by the Scarborough Blood Research Foundation in Maine to see if undetected or inadequately treated hypothyroidism in mothers during pregnancy was associated with low intelligence quotient (IQ) scores in offspring without neonatal hypothyroidism. The researchers measured serum thyroid stimulating hormone concentrations in 25,216 pregnant women between 1987 and 1990. Children born to mothers with normal or elevated thyroid stimulating hormone concentrations were then tested at age 7 to 9 years on 15 tests including: intelligence, language, attention, school performance, reading ability and visual-motor performance. No children in the study were found to have congenital hypothyroidism. According to the study, all children born to women with thyroid stimulating hormone concentrations at and above the 98th percentile had low scores on all 15 tests in this study. These children scored an average of 4 points lower on the Weil Wechsler Intelligence Scale for Children than the children born to 124 matched control women. Fifteen percent of the children born to women with low A had IQ scores equal to or below 85. The situation was worse for the 48 children born to women with untreated low A during pregnancy, who scored an average of 7 IQ points lower than the control group, and 19% of the children scored below 85. The researchers found that of the 62 women with elevated serum thyroid stimulating hormone concentrations, only 15 were diagnosed before pregnancy, and 14 of those were treated during pregnancy. 77% of the women with hypothyroidism had elevated serum anti-thyroid peroxidase antibody concentrations, suggesting chronic autoimmune thyroiditis. In a review accompanying the New England Journal of Medicine, Dr. Robert Uriger, associate editor of the journal, suggested that the cost of screening would be better spent on a population-wide effort to improve thyroid function by reducing iodine deficiency.