Children born to mothers with untreated hypothyroidism during pregnancy score lower on IQ tests than children of healthy mothers, according to a study conducted by Dr. James Haddow and partially funded by the National Institute of Child Health and Human Development (NICHD) and reported in the August 19 issue of the New England Journal of Medicine. However, children whose mothers were being treated for the condition scored almost the same as children born to healthy mothers. These findings suggest that early detection and treatment of hypothyroidism in pregnant women may be a critical part of prenatal care.
"We know that the health of the mother can be a key factor in her baby's health," said Duane Alexander, M.D., Director of the NICHD. "Fortunately, hypothyroidism is a condition that can be identified and treated during pregnancy. This study suggests that hypothyroidism might be added to the group of correctable maternal conditions that can influence the long-term health of the child," he said.
From 25,216 frozen serum samples obtained during pregnancy, researchers identified 62 women who had children between January 1987 and March 1990 and who, in retrospective analysis, were identified as having been hypothyroid during their pregnancies. These children were compared to a carefully matched group of 124 control children whose mothers' thyroid function in pregnancy was normal.
At the time of the study, the children ranged in age from 7 to 9 years. They participated in a series of 15 psychological tests relating to intelligence, attention, language, reading and school problems, and visual-motor performance.
The children born to mothers who were hypothyroid during pregnancy scored an
average of 4 points lower in IQ tests than the control children, and 15 percent
had IQ scores lower than 85, compared to only 5 percent of the control children
who scored that low. Overall, the case children scored poorer on all 15
individual tests than the chil
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NIH/National Institute of Child Health and Human Development