Does prenatal mild-to-moderate iodine deficiency lead to risk of intellectual disabilities in offspring?

July 16, 2020

Severe iodine deficiency in pregnancy has been linked to intellectual disabilities in offspring. An investigation studies whether the same is true for mild-to-moderate deficiency.

Previous research has shown that children born to mothers with severe iodine deficiency may have an increased risk of intellectual disability. An investigation in the Journal of Nutrition questions whether mild-to-moderate iodine deficiency during pregnancy can have a similar impact on neurodevelopmental issues.1

The investigators used 3 population-based birth cohorts: Generation R (n = 1634), INfancia y Medio Ambiente (n = 1293), and the Avon Longitudinal Study of Parents and Children (n = 2619). They excluded pre-existing thyroid disease, thyroid-interfering medication use, multiple fetuses, and fertility treatment. The average age for assessing a child for attention-deficit/hyperactivity disorder (ADHD) in the cohorts was 4.4 years to 7.7 years and for autistic traits it was 4.5 years to 7.6 years.

They found that urinary iodine-to-creatinine ratio (UI/Creat) <150 μg/g was not linked with ADHD or a high autistic-trait score. In early pregnancy, ≤18 weeks or ≤14 weeks of gestation, UI/Creat <150 μg/g wasn’t tied to a higher risk of behavioral issues. The link between a greater risk of ADHD and maternal free thyroxine was found to not be modified by iodine status.

The researchers concluded that there wasn’t evidence to support linking mild-to-moderate iodine deficiency with either ADHD or autistic traits. However, they did point out some limitations to their study including variability in iodine measurements used at different laboratories and the fact that ADHD and autistic train assessments were not performed at the same age and using the same assessment tools.

Reference

1. Levie D, Bath S, Guxens M, et al. Maternal iodine status during pregnancy is not consistently associated with attention-deficit hyperactivity disorder or autistic traits in children. J Nutr. 2020:150(6):1516-1528. doi:10.1093/jn/nxaa051