Iodine deficiency in pregnancy may have an adverse effect on children’s mental development, a study of around 1,000 mothers and their children published in The Lancet has revealed. The research raises concerns that the iodine status of pregnant women is a public health issue that needs to be addressed.
Although the potentially harmful effects of severe iodine deficiency on brain development are well-established, very few studies have examined the effect of mild or moderate iodine deficiency during pregnancy on cognitive development in the child. In their recent study conducted in some UK population groups, including pregnant women, a group of researchers from Surrey and Bristol universities, led by Prof. Margaret Rayman of the University of Surrey, in Guildford, UK-measured the iodine concentration in urine samples taken in the first trimester from 1040 pregnant women.
Following WHO guidelines on recommended concentrations of iodine during pregnancy, experts classified women who had an iodine-to-creatinine ratio of less than 150 ìg/g as being iodine deficient, and those with a ratio of 150 ìg/g or more as iodine sufficient. Over two thirds (67%) of the women fell into the category of less than 150 ìg/g.
Mental development of the children was assessed by measuring child IQ at age 8, and reading ability at age 9. Adjusting the results for external factors likely to affect these scores, such as parental education and breast-feeding, the researchers found that children of women in the iodine-deficient group were significantly more likely to have low scores of verbal IQ, reading accuracy, and reading comprehension. Moreover, the lower the mother’s concentration of iodine, the lower were the average scores for IQ and reading ability in the children.
According to Prof. Rayman, “Our results clearly show the importance of adequate iodine status during early pregnancy, and emphasise the risk that iodine deficiency can pose to the developing infant, even in a country classified as only mildly iodine deficient.”