Iodine deficiency during pregnancy: a national cross-sectional survey in Latvia

Objective: Low iodine intake during pregnancy may cause thyroid dysfunction, which results in inadequate fetal brain development. In the absence of a universal salt iodization programme, we conducted a nationwide survey of iodine deficiency in pregnant women in Latvia. Design: A countrywide twenty-cluster survey, with at least twenty women per cluster. Participants completed a questionnaire on dietary habits concerning iodine intake (n 739). Thyroid function (thyroid-stimulating hormone, free thyroxine and thyroperoxidase antibodies) was measured (n 550). Urinary iodine was measured using the ammonium persulfate method (n 696). Setting: The survey was performed in all regions of Latvia during the spring and autumn seasons in 2013. Subjects: Pregnant women (n 829). Results: The median creatinine (Cr)-standardized urinary iodine concentration (UIC) was 80.8 (interquartile range (IQR) 46.1-130.6) mu g/g Cr or 69.4 (IQR 53.992.6) mu g/l during pregnancy, and 81 % of pregnant women had UIC levels below the WHO recommended range of 150-250 mu g/g Cr. The UIC was lowest during the first trimester of pregnancy, 56.0 (IQR 36.4-100.6) mu g/g Cr, reaching higher concentrations of 87.5 (IQR 46.4-141.7) mu g/g Cr and 86.9 (IQR 53.8-140.6) mu g/g Cr in the second and third trimesters, respectively. Women taking supplements containing >= 150 mu g iodine (6.8 % of respondents) had non-significantly higher UIC than did women without supplementation (96.2 v. 80.3 mu g/g Cr, respectively, P = NS). Thyroperoxidase antibody concentration did not correlate significantly with UIC: Spearman's rho = -0.012, P = 0.78. Conclusions: The median UIC indicates iodine deficiency in pregnant women in Latvia. Iodine supplementation (150 mu g daily) and regular UIC monitoring should be suggested to overcome iodine deficiency and to reach the recommended levels without inducing autoimmune processes.