Iodine intake in pregnancy in Ireland - A cause for concern?

Background Adequate dietary iodine intake is necessary to maintain maternal thyroid function at a level permitting normal neuropsychological development of the foetus. Aims and Methods To determine dietary iodine status by measuring urinary iodine excretion (UIE), proportional to dietary intake, in Irish mothers during the first trimester of pregnancy. Results Median UIE showed seasonal variations, being lower in summer than in winter. The median values in pregnant women were, summer 45 mu g/l, winter 68 mu g/l. Equivalent values for controls were 43 and 91 mu g/l respectively UIE required to achieve WHO recommended daily iodine intakes would be 120-180 mu g/l. In the Irish subjects UIE values suggestive of iodine deficiency (<50 mu g/l) were observed in 55% of pregnant women tested in summer and 23% in winter Dairy milk iodine, a major dietary iodine source, showed similar variation. Conclusions While there is as yet no available evidence of widespread thyroid hypofunction in the Irish obstetric population, the findings are a cause of concern, which if confirmed by a more comprehensive investigation, may indicate the need for iodine prophylaxis.