Iodine supplementation in mildly iodine-deficient Thai pregnant women had no beneficial effect on offspring development
Keywords:Iodine supplementation, Pregnant women, Child development
Iodine deficiency during pregnancy causes detrimental effects on the offspring’s cognitive function. Supplementation of iodine in pregnant women is recommended worldwide but its long-term consequence is questioned. The objective of this study is to determine the effects of daily 200 µg iodine supplementation in Thai pregnant women on maternal iodine status and neurological development of children. Mildly iodine-deficient (median urinary iodine concentration, mUIC<150 µg/L) pregnant women were randomized to receive daily 200 µg iodine or placebo until term. Maternal UIC and thyroid function were measured throughout the study. For child development test; Neonatal Behavioral Assessment Scale (NBAS) was performed at 6-week: Bayley Scales of Infant Development (BSID)-III was applied at 1 and 2 years: Wechsler Preschool and Primary Scale of Intelligence (WPPSI)-III was tested for 5-6 years children intelligence quotient (IQ). Audiogram of 5-6 years old children was obtained using Audiometer (GSI 61). Five hundred and fourteen pregnant women participated in the study (263 in control group and 251 in iodine group) at mean gestational age of 11 weeks. At 3rd trimester, two-fold significant increase of maternal mUIC in iodine group was reported (p<0.001) while mUIC in placebo group remained unchanged (p>0.05). Maternal thyroid function in both groups was stable and within normal range during the study. There were no significant differences in prevalence of maternal thyroid dysfunction between the two groups (p>0.05). Median UIC of children was higher than the recommendation (100 µg/L) and no significant differences were seen between the groups at every timepoints (p>0.05). All cognitive function scores in children did not differ significantly between groups (p>0.05). There were no significant differences in audiogram scores between the two groups (p>0.05). Supplementation of 200 µg iodine per day in mildly iodine-deficient Thai pregnant women improved maternal iodine intake but had no effect on long-term child neurodevelopment. However, iodine supplements for pregnant women should continue to be recommended until the impact of universal salt iodization (USI) program on Thai women is clarified.
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