Background The effect of mild-to-moderate maternal iodine deficiency on the neuropsychological development of their offspring is uncertain. We aimed to assess the association between iodine status during pregnancy and the cognitive and motor development of children at 4–5 years.
Methods We conducted a prospective cohort study in four Spanish regions with recruitment of pregnant women between 2003 and 2008 and follow-up of their children up to 4–5 years (mean (SD)=4.8 (0.6)). Cognitive and motor function was assessed in 1803 children using the McCarthy Scales of Children’s Abilities. Dietary iodine and supplementation were measured through questionnaires twice during pregnancy. Urinary iodine concentration (UIC) was measured in spot samples. The residuals of a regression of UIC against creatinine were used to define a variable corrected for creatinine (UIC~Cr).
Results Neither iodine supplements nor iodised salt consumption or maternal UIC were associated with cognitive or motor function. After adjusting for creatinine, children of women with UIC~Cr <100 µg/L had 3.93 (95% CI −6.18 to –1.69) general cognitive scores lower than the reference (150–249 µg/L). Dietary iodine was inversely associated with motor scores and milk but not other dairy products or seafood consumption accounted for this association (beta: −1.36; 95% CI −2.12 to –0.61; per one daily milk serving).
Conclusions We found an association between low maternal urinary iodine and lower cognitive scores in childhood, although only when corrected for creatinine, adding to the evidence that iodine deficiency may have potential harmful effects on neurodevelopment. Iodine supplementation does not appear to improve child’s neurodevelopment at 4–5 years.
- longitudinal studies
- public health policy
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Contributors MM, ME, JJ, JI and MR designed the research; ME, SL, M-JL-E, MB, IR, LG, MA-P and AT conducted the research; MM and JV analysed the data; MM and MR wrote the paper and had primary responsibility for final content. All authors read and approved the final manuscript.
Funding This work was supported by grants from the European Union: NEW GENERIS FP6-2003-Food-3-A-016320, FP7-ENV-2011 cod 282957, HEALTH.2010.2.4.5-1; Spain: Instituto de Salud Carlos III (G03/176, CB06/02/0041; FIS-FEDER: 04/2018, 04/1436, 05/1079, 07/0314, 08/1151, 09/02311, 11/01007, 11/02591, 11/02038, 13/1944, 13/02429, 14/00891 and 14/01687 and Miguel Servet-FEDER CP11/00178, CP15/00025); Generalitat Valenciana: FISABIO (UGP 15-230, UGP-15-244 and UGP-15-249); Generalitat de Catalunya (CIRIT 1999SGR 00241); Department of Health of the Basque Government (2005111093 and 2009111069); the Provincial Government of Gipuzkoa (DFG06/004 and DFG08/001); Obra Social Cajastur; and University of Oviedo.
Competing interests None declared.
Ethics approval The Hospital Ethics Committees of each area approved the research protocol: Hospital La Fe de Valencia, Hospital de Sabadell – Corporació Parc Taulí or Hospital de Terrassa, Hospital Universitario Central de Oviedo and Hospital de Cruces in Barakaldo.
Provenance and peer review Not commissioned; externally peer reviewed.