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01-12-2020 | Research article

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

Authors: Charles Jonathan Peter Snart, Diane Erin Threapleton, Claire Keeble, Elizabeth Taylor, Dagmar Waiblinger, Stephen Reid, Nisreen A. Alwan, Dan Mason, Rafaq Azad, Janet Elizabeth Cade, Nigel A. B. Simpson, Sarah Meadows, Amanda McKillion, Gillian Santorelli, Amanda H. Waterman, Michael Zimmermann, Paul M. Stewart, John Wright, Mark Mon-Williams, Darren Charles Greenwood, Laura J. Hardie

Published in: BMC Medicine | Issue 1/2020

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.

Available only for authorised users

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Title: Maternal iodine status, intrauterine growth, birth outcomes and congenital anomalies in a UK birth cohort
Authors: Charles Jonathan Peter Snart
Diane Erin Threapleton
Claire Keeble
Elizabeth Taylor
Dagmar Waiblinger
Stephen Reid
Nisreen A. Alwan
Dan Mason
Rafaq Azad
Janet Elizabeth Cade
Nigel A. B. Simpson
Sarah Meadows
Amanda McKillion
Gillian Santorelli
Amanda H. Waterman
Michael Zimmermann
Paul M. Stewart
John Wright
Mark Mon-Williams
Darren Charles Greenwood
Laura J. Hardie
Publication date: 01-12-2020
Publisher: BioMed Central
Published in: BMC Medicine / Issue 1/2020
Electronic ISSN: 1741-7015
DOI: https://doi.org/10.1186/s12916-020-01602-0

At a glance: The ONWARDS insulin icodec trials

Springer Medicine

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

Abstract

Background

Methods

Results

Conclusion

Trial registration

At a glance: The ONWARDS insulin icodec trials

Springer Medicine

Abstract

Background

Methods

Results

Conclusion

Trial registration

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