Effect of Iodine Supplementation During Pregnancy on Infant Neurodevelopment at 1 Year of Age

Abstract

Iodine is the main constituent of thyroid hormones, which in turn are required for fetal brain development. However, the relation between iodine intake during pregnancy, thyroid function, and child neurodevelopment needs further evaluation. The authors assessed the association of maternal iodine intake from diet and supplements during pregnancy and of maternal and neonatal thyroid function with infant neurodevelopment. The Mental Development Index and Psychomotor Development Index (PDI) for 691 children were obtained between 2005 and 2007 using the Bayley Scales of Infant Development at age 1 year in a prebirth cohort in Valencia, Spain. In multivariate analyses, a maternal thyrotropin level >4 μU/mL was associated with an increased risk of a PDI <85 (odds ratio = 3.5, P = 0.02). Maternal intake of ≥150 μg/day, compared with <100 μg/day, of iodine from supplements was associated with a 5.2-point decrease in PDI (95% confidence interval: -8.1, -2.2) and a 1.8-fold increase in the odds of a PDI <85 (95% confidence interval: 1.0, 3.3). When analyses were stratified by sex, this association was intensified for girls but was not observed for boys. Further evidence on the safety and effectiveness of iodine supplementation during pregnancy is needed before it is systematically recommended in iodine-sufficient or mildly deficient areas.

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).…”

The Role of Nutrition in Children's Neurocognitive Development, From Pregnancy Through Childhood

“…Velasco et al (2009) also found that those infants whose mothers took daily iodine supplements from the first trimester of pregnancy exhibited better psychomotor development (measured on the Bayley Scales of Infant Development), compared to those whose mothers were not supplemented with groups evaluated at different ages (5.5 and 12.4 months, respectively). Contrary to expectation, another study from Spain reported lower psychomotor development (measured on the Bayley Scale of Infant Development) in infants (especially in girls) born to mothers with maternal multivitamin supplementation that contained high amounts of iodine (100-149 μg/day), when compared to those infants with lesser amounts of maternal iodine supplementation (<100 μg/day) (Murcia et al, 2011). It is possible that the optimum dose of iodine for those mothers who are manifesting only mild iodine deficiency is less; further research is needed to determine the safe level of iodine intake for mildly deficient pregnant women.…”

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).…”