The effect of iodine supplementation in pregnancy on early childhood neurodevelopment and clinical outcomes: results of an aborted randomised placebo-controlled trial.

Shao J Zhou,Lex W Doyle,Andrew J Mcphee,Peter J Anderson,Louise Kornman,Sheila A Skeaff,Maria Makrides,Lisa N Yelland,Philip Ryan

doi:10.1186/s13063-015-1080-8

Abstract

BackgroundConcern that mild iodine deficiency in pregnancy may adversely affect neurodevelopment of offspring has led to recommendations for iodine supplementation in the absence of evidence from randomised controlled trials. The primary objective of the study was to investigate the effect of iodine supplementation during pregnancy on childhood neurodevelopment. Secondary outcomes included pregnancy outcomes, maternal thyroid function and general health.MethodsWomen with a singleton pregnancy of fewer than 20 weeks were randomly assigned to iodine (150 μg/d) or placebo from trial entry to birth. Childhood neurodevelopment was assessed at 18 months by using Bayley Scales of Infant and Toddler Development (Bayley-III). Iodine status and thyroid function were assessed at baseline and at 36 weeks’ gestation. Pregnancy outcomes were collected from medical records.ResultsThe trial was stopped after 59 women were randomly assigned following withdrawal of support by the funding body. There were no differences in childhood neurodevelopmental scores between the iodine treated and placebo groups. The mean cognitive, language and motor scores on the Bayley-III (iodine versus placebo, respectively) were 99.4 ± 12.2 versus 101.7 ± 8.2 (mean difference (MD) −2.3, 95 % confidence interval (CI) −7.8, 3.2; P = 0.42), 97.2 ± 12.2 versus 97.9 ± 11.5 (MD −0.7, 95 % CI −7.0, 5.6; P = 0.83) and 93.9 ± 10.8 versus 92.4 ± 9.7 (MD 1.4, 95 % CI −4.0, 6.9; P = 0.61), respectively. No differences were identified between groups in any secondary outcomes.ConclusionsIodine supplementation in pregnancy did not result in better childhood neurodevelopment in this small trial. Adequately powered randomised controlled trials are needed to provide conclusive evidence regarding the effect of iodine supplementation in pregnancy.Trials registrationThe trial was registered with the Australian New Zealand Clinical Trials Registry at http://www.anzctr.org.au. The registration number of this trial is ACTRN12610000411044. The trial was registered on 21 May 2010.

Highlights

Concern that mild iodine deficiency in pregnancy may adversely affect neurodevelopment of offspring has led to recommendations for iodine supplementation in the absence of evidence from randomised controlled trials
A recent systematic review of randomised controlled trials (RCTs) highlighted that the effect of iodine supplementation in pregnancy in regions with mild to moderate iodine deficiency is unclear because none of the RCTs conducted in those regions assessed developmental outcomes of children [3]
The aim of the study was to assess the effect of iodine supplementation in pregnancy over and above the mandatory iodine fortification on childhood neurodevelopment and other clinical outcomes, including pregnancy outcomes, maternal thyroid function, mental health and general well-being

Summary

Introduction

Concern that mild iodine deficiency in pregnancy may adversely affect neurodevelopment of offspring has led to recommendations for iodine supplementation in the absence of evidence from randomised controlled trials. There is increasing concern that mild to moderate iodine deficiency during pregnancy—which has emerged as a public health issue in a number of developed countries, including Australia and the UK—may lead to cognitive deficits and learning disability in children. Adverse effects on child development in relation to iodine supplementation in pregnancy have been reported from cohort studies [5]. These emerging data have been differentially interpreted by expert groups and government authorities worldwide, resulting in various approaches to address this public health issue

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