This is a well regarded extensive UK study . . .
http://www.thejournal.ie/iodine-defi...19382-May2013/
‘Children of the 90s’ research
Researchers used samples and data from Bristol-based Avon Longitudinal Study of Parents and Children (ALSPAC), also known as ‘Children of the 90s’. This is a long-term project involved more than
14,000 pregnant women in 1991 and 1992, and the health and development of their children has been followed by scientists ever since.
Researchers measured the iodine concentration in urine samples taken in the first trimester from 1,040 pregnant women. Referring to World Health Organisation (WHO) guidelines on recommended concentrations of iodine during pregnancy, they classified women who had an iodine-to-creatinine ratio [1] of less than 150 μg/g as being iodine deficient, and those with a ratio of 150 μg/g or more as iodine sufficient.
Over two thirds (67 per cent) of the women fell into the category of “iodine deficient”.
The babies born underwent mental development assessments which involved measuring child IQ at age eight and reading ability at age nine. 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 (lower quartile) of verbal IQ, reading accuracy, and reading comprehension. The research, published in the Lancet medical journal, found that the lower the mother’s concentration of iodine, the lower were the average scores for IQ and reading ability in the children.