It is well known that severe iodine deficiency during pregnancy may cause impaired
brain development in the child, with effects on cognitive and motor function, hearing
and speech. Whether mild-to-moderate deficiency also affects neurological development
is less well known, but in the past decade a number of observational studies have
been conducted to answer this question and these studies are reviewed in this article.
The picture is now emerging that even mild-to-moderate iodine deficiency during pregnancy
may be associated with subtle impairments in cognition and school performance, although
the evidence from randomised controlled trials is still lacking. As global efforts
to eradicate iodine deficiency in populations continue, it is more likely that mild-to-moderate,
rather than severe, iodine deficiency will be the issue of concern in pregnancy, and
therefore further research in regions of mild-to-moderate deficiency is required to
strengthen the research base and to inform public-health policy.