The importance of iodine nutrition during pregnancy.

OBJECTIVE To examine the importance of iodine nutrition during pregnancy. DESIGN Review of existing literature of iodine in pregnancy. SETTING Population surveys and metabolic studies. SUBJECTS Pregnant women. RESULTS The main changes in thyroid function associated with pregnancy are due to an increase in hormone requirements that begin in the first trimester of gestation. This increase can only be met by a proportional increase in hormone production, something that depends directly upon the availability of iodine. When dietary iodine is lacking, an adequate physiological adaptation is difficult to achieve and is progressively replaced by pathological alterations that occur in parallel with the degree and duration of iodine deprivation. CONCLUSIONS Iodine prophylaxis should be given systematically to women during pregnancy. In most public health programmes dealing with the correction of iodine deficiency disorders, iodised salt has been used as the preferred means to deliver iodine to households. Iodised salt, however, is not the ideal means of delivering iodine in the specific instances of pregnancy, breast-feeding and complementary feeding because of the need to limit salt intake during these periods. In European countries, presently it is proposed that iodine is given to pregnant women and breast-feeding mothers by systematically administering multivitamin tablets containing iodine in order to reach the recommended dietary allowance of 250 microg iodine day-1.