Mild iodine deficiency during pregnancy can have long-term adverse impacts on neurocognition and educational outcomes in children

Even mild iodine deficiency during pregnancy could lead to long-term negative impacts on fetal neurocognition that are not ameliorated by iodine deficiency during childhood. Although mandatory fortification in some countries such as Australia may have led to sufficiency in the general population, pregnant women are still at risk of deficiency, resulting in long-term irreversible but preventable consequences for their offspring.

Iodine is important for neurodevelopment in utero and in childhood. Iodine deficiency results in a spectrum of disorders with many speculating that even mild maternal iron deficiency has subtle impacts on fetal development. Severe iodine deficiency during gestation is linked with neurocognitive sequelae. However, it remains unclear that low maternal dietary iodine intake in areas of mild deficiency leads to measurable effects on cognition and neurodevelopment of the offspring. Moreover, clinical trials have not examined long-term developmental consequences in the offspring. This study was conducted to investigate if mild gestational iron deficiency had long-term effects on educational outcomes. Specifically, it was designed to determine if children born to mothers with urinary iodine concentrations < 150 μg/L during pregnancy had poorer educational outcomes in primary school than peers whose mothers did not have gestational iron deficiency.

This was a longitudinal follow-up of the Gestational Iodine Cohort. Pregnancy occurred during a period of mild iron deficiency in the population, with the children subsequently growing up in an iodine-replete environment. Participants were children whose mothers attended The Royal Hobart Hospital antenatal clinics between 1999 and 2001. There were no significant differences (P < .05) between the 2 groups in any characteristics measured during gestation and birth. Children born to mothers with insufficient iodine nutrition (< 150 μg/L) had poorer educational outcomes. National and State standardized testing revealed that children whose mothers had urinary iodine concentration < 150 μg/L had reductions in scores of 10% in spelling, 7.6% in grammar and 5.7% in English-literacy performance compared with children whose mothers’ urinary iodine concentrations were ≥ 150 μg/L. These associations remained significant after adjustment for a range of biological factors. Differences in spelling remained significant after further adjustment for socioeconomic factors.

In conclusion, even mild iodine deficiency during pregnancy could lead to long-term negative impacts on fetal neurocognition that are not ameliorated by iodine supplementation during childhood. Although mandatory fortification in some countries such as Australia may have led to sufficiency in the general population, pregnant women are still at risk of deficiency, resulting in long-term irreversible but preventable consequences for their offspring.

References

  1. Hynes, K.L., et al., Mild iodine deficiency during pregnancy is associated with reduced educational outcomes in the offspring: 9-year follow-up of the gestational iodine cohort. J Clin Endocrinol Metab, 2013. 98(5): p. 1954-62.