Iodine Supplementation During Pregnancy and Infant Neuropsychological Development: INMA Mother and Child Cohort Study

Abstract

Iodine supplementation during pregnancy is a common practice in developed countries. However, scant evidence is available regarding the safety and effectiveness of maternal iodine supplementation with regard to child neuropsychological development. We previously reported an inverse association between iodine supplementation and the psychomotor development of infants in a birth cohort from Valencia, Spain. In the present study, we assessed this association in a wider sample of mother and child pairs from 3 other regions in Spain. Neuropsychological development was assessed using the Bayley Scales of Infant Development in 1,519 infants (median age, 16 months) between 2006 and 2009. In multivariate analyses, maternal consumption of 150 μg/day or more of iodine from supplements was related to a 1.5-fold increase in the odds of a psychomotor score less than 85 (95% confidence interval: 0.8, 2.9) and to a 1.7-fold increase in the odds of a mental score less than 85 (95% confidence interval: 0.9, 3.0). Findings previously reported in the Valencia cohort were only partially verified. The results of the present study suggest that, at least in these regions, iodine supplementation does not improve infant neuropsychological development at 1 year of age. Further research is needed on the risks and benefits of supplementary iodine for both maternal thyroid function and child neurodevelopment.

Suboptimal Maternal Iodine Intake Is Associated with Impaired Child Neurodevelopment at 3 Years of Age in the Norwegian Mother and Child Cohort Study

“…In this study we examined the associations in women with iodine intake from food below and above the EAR (160 mg/d) separately because the effect of supplemental iodine might depend on previous iodine status. Our findings of no beneficial effects and some indications of negative effects are supported by findings from the Environment and Childhood cohort in Spain in which an increased risk of low psychomotor (10,11) and mental scores (11) in children of women who reported intake of iodine from supplements $150 mg/d compared with <100 mg/d was observed. On the other hand, Velasco et al (49) reported a positive impact on psychomotor scores in children of mothers who received 300 mg I from supplements from the first trimester compared with controls in a nonrandomized intervention study.…”

“…There is, however, a lack of evidence to support the recommendation for iodine supplements during pregnancy in areas with mild-to-moderate ID, and some studies have even indicated that supplemental iodine is associated with adverse effects on child neurodevelopment (10,11).…”

THERAPY OF ENDOCRINE DISEASE: Impact of iodine supplementation in mild-to-moderate iodine deficiency: systematic review and meta-analysis

“…Nine RCTs (24,25,26,27,28,29,30,31,32) and eight observational studies (33,34,35,36,37,38,39,40) were included in the review. Seven RCTs were reported on the effects of maternal supplementation on maternal thyroid function (26,27,28,29,30,31,32,33,34,35,36,37,38,39,40). Of these, four RCTs also contained data on neonatal thyroid function (27,29,30,32).…”

CONTROVERSIES IN ENDOCRINOLOGY: On the need for universal thyroid screening in pregnant women

“…In this latter study, as well as in others (36), the psychomotor development of these children was improved thus supporting iodine supplementation. Finally, a recent observational study has reported an association of low FT 4 with worse neurocognitive tests in daughters of mothers receiving potassium iodide supplementation during pregnancy (113,114). Taking all these data together, the more prudent position right now is not to treat isolated hypothyroxinemia due to the lack of evidence (115) of its effect and the inconsistency of FT 4 measurements, but to ensure sufficient iodine supply during and, even better, before pregnancy.…”