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

Double-blind, placebo-controlled multicenter randomized controlled trial. Participants: pregnant women with singleton pregnancy <20 weeks gestation; excluded if taking iodine-containing supplements, had thyroid disease, drug or alcohol abuse, fetus with major abnormality, or English not the main language.

Iodine 150 micrograms per day as potassium iodide, one tablet daily from trial entry to birth.

Iodine supplementation during pregnancy did not improve childhood neurodevelopment at 18 months compared with placebo. Bayley-III cognitive, language, and motor composites showed no clinically meaningful differences: cognitive 99.4 vs 101.7 (MD -2.3; 95% CI -7.8 to 3.2; P=0.42); language 97.2 vs 97.9 (MD -0.7; 95% CI -7.0 to 5.6; P=0.83); motor 93.9 vs 92.4 (MD 1.4; 95% CI -4.0 to 6.9; P=0.61). No differences in secondary outcomes. Conclusion: There is no evidence of neurodevelopmental benefit from routine iodine supplementation in pregnancy in this small trial; adequately powered randomized trials are needed to determine efficacy.

Early termination with a small sample size limits statistical power; limited generalizability to other populations; imbalance in infant sex between groups; unblinding due to funding withdrawal and post-unblinding changes in supplementation.