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

Abstract

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 45microg/l, winter 68microg/l. Equivalent values for controls were 43 and 91microg/l respectively. UIE required to achieve WHO recommended daily iodine intakes would be 120-180microg/l. In the Irish subjects UIE values suggestive of iodine deficiency (<50microg/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.