The Importance of Iodine Supplementation and Smoking for Maternal and Fetal Thyroid Health in Pregnant Women

presented study, 150 μg/day iodine supple-mentation was started in the first trimester. We think this dose may be regarded as in-adequate iodine supplementation. In addi-tion, urinary iodine excretion in the third trimester was significantly lower in smok-ers, but this finding was not discussed properly. In another study among women of childbearing age, urinary iodine excre-tion in heavy cigarette smokers was found to be increased, and an association was ob-served between smoking and hypothyrox-inemia [3] . It was advised that iodine sup-plementation in smoking women of child-bearing age should be done carefully. Because impaired renal function may affect urinary iodine excretion, renal func-tion in the presented study could have been assessed at least with serum creatinine lev-els or with spot urine analysis. Also, smok-ing has been proposed to decrease not only anti-Tg but also anti-TPO, and therefore smoking might reduce the risk of thyroid autoimmunity [4, 5] . In the presented study, the authors indicated only the status of anti-Tg. Serum cotinine levels in smok-ers increase in direct proportion to the Dear Editor, We read the article ‘Relative impact of iodine supplementation and maternal smoking on cord blood thyroglobulin in pregnant women with normal thyroid function’ by Hieronimus et al. [1] with great interest. The authors concluded that iodine supplementation does not signifi-cantly impact cord blood (CB) thyroglobu-lin (Tg) in healthy nonsmoking pregnant women selected for normal thyroid func-tion, as opposed to smoking women, and stated that CB Tg appears to be a marker of in utero tobacco exposure. They proposed that in areas of mild iodine deficiency,iodine supplementation could especially benefit the fetuses of smokers. We would like to thank the authors for their contribu-tion which we believe will be a source of inspiration for further studies. Once-daily prenatal vitamins should contain 150–200 μg iodine. 250 μg daily io-dine intake is recommended during preg-nancy and in the lactation period. The ad-equacy of the iodine intake during preg-nancy can be assessed by measuring urinary iodine concentration, which should ideally range between 150 and 250 μg/l [2] . In the