The importance of iodine supplementation and smoking for maternal and fetal thyroid health in pregnant women.

presented study, 150 μg/day iodine supplementation was started in the first trimester. We think this dose may be regarded as inadequate iodine supplementation. In addition, urinary iodine excretion in the third trimester was significantly lower in smokers, but this finding was not discussed properly. In another study among women of childbearing age, urinary iodine excretion in heavy cigarette smokers was found to be increased, and an association was observed between smoking and hypothyroxinemia [3] . It was advised that iodine supplementation in smoking women of childbearing age should be done carefully. Because impaired renal function may affect urinary iodine excretion, renal function in the presented study could have been assessed at least with serum creatinine levels or with spot urine analysis. Also, smoking 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 smokers 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 Hiéronimus et al. [1] with great interest. The authors concluded that iodine supplementation does not significantly impact cord blood (CB) thyroglobulin (Tg) in healthy nonsmoking pregnant women selected for normal thyroid function, 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 contribution 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 iodine intake is recommended during pregnancy and in the lactation period. The adequacy of the iodine intake during pregnancy can be assessed by measuring urinary iodine concentration, which should ideally range between 150 and 250 μg/l [2] . In the Received: January 7, 2013 Accepted after revision: April 2, 2013 Published online: July 16, 2013