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Maternal iodine status, intrauterine growth, birth outcomes and congenital anomalies in a UK birth cohort.

Published version
Peer-reviewed

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Authors

Snart, Charles Jonathan Peter 
Threapleton, Diane Erin 
Keeble, Claire 
Taylor, Elizabeth 
Waiblinger, Dagmar 

Abstract

BACKGROUND: Severe iodine insufficiency in pregnancy has significant consequences, but there is inadequate evidence to indicate what constitutes mild or moderate insufficiency, in terms of observed detrimental effects on pregnancy or birth outcomes. A limited number of studies have examined iodine status and birth outcomes, finding inconsistent evidence for specific outcomes. METHODS: Maternal iodine status was estimated from spot urine samples collected at 26-28 weeks' gestation from 6971 mothers in the Born in Bradford birth cohort. Associations with outcomes were examined for both urinary iodine concentration (UIC) and iodine-to-creatinine ratio (I:Cr). Outcomes assessed included customised birthweight (primary outcome), birthweight, small for gestational age (SGA), low birthweight, head circumference and APGAR score. RESULTS: There was a small positive association between I:Cr and birthweight in adjusted analyses. For a typical participant, the predicted birthweight centile at the 25th percentile of I:Cr (59 μg/g) was 2.7 percentage points lower than that at the 75th percentile of I:Cr (121 μg/g) (99% confidence interval (CI) 0.8 to 4.6), birthweight was predicted to be 41 g lower (99% CI 13 to 69) and the predicted probability of SGA was 1.9 percentage points higher (99% CI 0.0 to 3.7). There was no evidence of associations using UIC or other birth outcomes, including stillbirth, preterm birth, ultrasound growth measures or congenital anomalies. CONCLUSION: Lower maternal iodine status was associated with lower birthweight and greater probability of SGA. Whilst small, the effect size for lower iodine on birthweight is comparable to environmental tobacco smoke exposure. Iodine insufficiency is avoidable, and strategies to avoid deficiency in women of reproductive age should be considered. TRIAL REGISTRATION: ClinicalTrials.gov NCT03552341. Registered on June 11, 2018.

Description

Keywords

Birthweight, Insufficiency, Iodine, Pregnancy, SGA, Adult, Birth Weight, Congenital Abnormalities, Female, Fetal Growth Retardation, Humans, Infant, Newborn, Iodine, Male, Mothers, Pregnancy, Pregnancy Outcome, United Kingdom

Journal Title

BMC Med

Conference Name

Journal ISSN

1741-7015
1741-7015

Volume Title

18

Publisher

Springer Science and Business Media LLC
Sponsorship
National Institute for Health Research (UK) (PR-R10-0514-11004)