Iodine Status in Pregnancy and Associated Health Outcomes

NCT ID: NCT03552341

Last Updated: 2021-10-14

Basic Information

• Recruitment Status: COMPLETED
• Total Enrollment: 246 participants
• Study Classification: OBSERVATIONAL
• Study Start Date: 2016-02-01
• Study Completion Date: 2019-03-31

Brief Summary

Iodine is a key micronutrient in the diet, essential for healthy growth, and is particularly important during pregnancy and breastfeeding when demands are increased to support the developing baby. Many people are thought to lack all the iodine they need, and this is a greater issue during and shortly after pregnancy when the body's iodine requirements are greatest. Iodine deficiency complications are potentially serious for both mother and child. Iodine deficiency can lead to thyroid enlargement, lower production of important hormones produced by the thyroid, pregnancy complications in the mother, and impaired growth and developmental problems in babies and children. This research will focus on providing an up-to-date estimate of how many pregnant women do not have enough iodine, and what different levels of iodine might mean in terms of health risks during pregnancy and for childhood development. The investigators will investigate how iodine levels vary over the course of pregnancy and lactation, how this is affected by diet, associated changes in thyroid size and function, and what levels of iodine are linked with greater risk of subsequent health problems. The research will take advantage of existing urine samples collected from mothers during pregnancy in the Born in Bradford birth cohort study, where the investigators also know of any adverse pregnancy outcomes, as well as any developmental problems for the baby and in early childhood.

Detailed Description

Background: Pregnant women may be particularly vulnerable to iodine deficiency as requirements increase to support fetal development. There is limited information concerning how maternal iodine status changes during pregnancy. Severe iodine deficiency is associated with deleterious health outcomes during pregnancy including gestational diabetes, preeclampsia, stillbirth, and increased mortality. For the fetus, severe iodine deficiency results in reduced birthweight, increased mortality and neurodevelopmental issues. Several studies suggest 40% of pregnant mothers in the United Kingdom (UK) may not meet the World Health Organization (WHO) definition of iodine sufficiency. Although the effects of severe iodine deficiency are known, the impact of mild-to-moderate deficiencies on maternal health and associated fetal and childhood development are not well understood.

Aims:

1. To provide up-to-date information on iodine status in pregnant women in the UK, including changes during pregnancy and lactation, and the role of diet.

2. To quantify any associations between iodine status during pregnancy, pregnancy outcomes, and cognitive and motor development of the child.

3. To compare the iodine status of mothers in the Born in Bradford cohort to a more nationally representative sample.

Research plan and methods: The investigators will utilize the Born in Bradford (BiB) birth cohort which recruited over 12000 pregnant women between 2007- 2009, and has deposited in a biobank 6971 spot urine samples collected at 26-28 weeks gestation.

Data are available on health outcomes during pregnancy including gestational diabetes, preeclampsia, blood pressure, length of gestation, mortality, mental health. Child outcome measures at birth include weight, length, head circumference, small-for-gestational-age. Childhood developmental measures include height, weight, growth trajectories, motor skills, literacy, numeracy and mental health (Strengths and Difficulties Questionnaire, SDQ). Linkage with educational outcomes has been achieved, including Early Years Foundation Stage (EYFS) outcomes and Standard Assessment Tests (SATS) at both Key Stage 1 (KS1) and Key Stage 2 (KS2).

The investigators will measure all maternal urine samples in BiB to allow sufficient power to detect potential modest-sized associations. This will be conducted using Inductively Coupled Plasma Mass Spectrometry (ICPMS). All maternal baseline characteristics and associated outcome data are available for extraction from the primary BiB database.

The investigators will apply multiple logistic regression and multiple linear regression to ascertain potential associations between maternal iodine status and health and developmental outcomes. Cubic splines will be used to model any nonlinear dose-response associations, making no assumptions regarding any predefined thresholds.

The investigators will also conduct a longitudinal substudy to ascertain how iodine status varies between trimesters (The Hiba study). 200 pregnant women will be recruited at 12 week dating scans and the following collected: baseline characteristics, urine samples for iodide analysis, blood for thyroid stimulating hormone (TSH), free thyroxine (fT4) and triiodothyronine (fT3), thyroglobulin, Glomerular Filtration Rate (GFR) based on serum creatinine, visual inspection of the thyroid using standard methods, dietary intake using a validated online 24h recall tool (myfood24). Data collection will be repeated at 26 and 36 weeks' gestation, and 6, 18 and 30 weeks postpartum. The proposed substudy will clarify how iodine status alters in pregnancy and lactation, and any associated thyroid hormone changes. The investigators will identify key sources of iodine in the diet and ascertain dietary patterns associated with different iodine status. To compare results to a more nationally representative sample, spot urines will be analysed from approximately 650 women in the SCOPE birth-cohort (London, Leeds and Manchester).

Conditions

Cognitive Developmental Delay; Birth Weight

Study Design

• Observational Model Type: COHORT
• Study Time Perspective: PROSPECTIVE

Interventions

Maternal iodine status

Urinary iodine concentration during pregnancy at 26 weeks' gestation (Bord in Bradford study) and at 12, 26 and 36 weeks' gestation, 6, 18 and 30 weeks postpartum (Hiba longitudinal study). This is primarily in the form of Iodine to Creatinine ratio, to take spot urine volume into account. There is no intervention in this observational study.

Intervention Type: OTHER

Eligibility Criteria

Inclusion Criteria

• Female (Both Born in Bradford and Hiba longitudinal cohorts)
• Able to provide informed consent (Both Born in Bradford and Hiba longitudinal cohorts)
• Confirmed pregnant at 26-28 week Oral Glucose Tolerance Test (OGTT) (Born in Bradford cohort)
• Confirmed 9-15 weeks pregnant at 12 week dating scan (Hiba longitudinal cohort)
• Aged 18-40 years (Hiba longitudinal cohort)
• No medical or known first degree family history of a thyroid condition (Hiba longitudinal cohort).

Exclusion Criteria

• Inability to provide informed consent (Both Born in Bradford and Hiba longitudinal cohorts)
• Current or former medical history of thyroid disease (Hiba longitudinal cohort)
• Use of thyroid related medications (Hiba longitudinal cohort)

• Minimum Eligible Age: 18 Years
• Maximum Eligible Age: 40 Years
• Eligible Sex: FEMALE
• Accepts Healthy Volunteers: No

Sponsors

Bradford Teaching Hospitals NHS Foundation Trust

OTHER_GOV

Sponsor Role: collaborator

University of Leeds

OTHER

Sponsor Role: lead

Responsible Party

Darren Greenwood

Senior Lecturer in Biostatistics

Responsibility Role: PRINCIPAL_INVESTIGATOR

Principal Investigators

Darren C Greenwood, PhD

Role: PRINCIPAL_INVESTIGATOR

University of Leeds

Laura J Hardie, PhD

Role: PRINCIPAL_INVESTIGATOR

University of Leeds

References

Snart CJP, Keeble C, Taylor E, Cade JE, Stewart PM, Zimmermann M, Reid S, Threapleton DE, Poston L, Myers JE, Simpson NAB, Greenwood DC, Hardie LJ. Maternal Iodine Status and Associations with Birth Outcomes in Three Major Cities in the United Kingdom. Nutrients. 2019 Feb 20;11(2):441. doi: 10.3390/nu11020441.

Reference Type: RESULT

PMID: 30791590 (View on PubMed)

Snart CJP, Threapleton DE, Keeble C, Taylor E, Waiblinger D, Reid S, Alwan NA, Mason D, Azad R, Cade JE, Simpson NAB, Meadows S, McKillion A, Santorelli G, Waterman AH, Zimmermann M, Stewart PM, Wright J, Mon-Williams M, Greenwood DC, Hardie LJ. Maternal iodine status, intrauterine growth, birth outcomes and congenital anomalies in a UK birth cohort. BMC Med. 2020 Jun 11;18(1):132. doi: 10.1186/s12916-020-01602-0.

Reference Type: RESULT

PMID: 32522280 (View on PubMed)

Threapleton DE, Snart CJP, Keeble C, Waterman AH, Taylor E, Mason D, Reid S, Azad R, Hill LJB, Meadows S, McKillion A, Alwan NA, Cade JE, Simpson NAB, Stewart PM, Zimmermann M, Wright J, Waiblinger D, Mon-Williams M, Hardie LJ, Greenwood DC. Maternal iodine status in a multi-ethnic UK birth cohort: Associations with child cognitive and educational development. Paediatr Perinat Epidemiol. 2021 Mar;35(2):236-246. doi: 10.1111/ppe.12719. Epub 2020 Sep 1.

Reference Type: RESULT

PMID: 32870514 (View on PubMed)

Threapleton DE, Waiblinger D, Snart CJP, Taylor E, Keeble C, Ashraf S, Bi S, Ajjan R, Azad R, Hancock N, Mason D, Reid S, Cromie KJ, Alwan NA, Zimmermann M, Stewart PM, Simpson NAB, Wright J, Cade JE, Hardie LJ, Greenwood DC. Prenatal and Postpartum Maternal Iodide Intake from Diet and Supplements, Urinary Iodine and Thyroid Hormone Concentrations in a Region of the United Kingdom with Mild-to-Moderate Iodine Deficiency. Nutrients. 2021 Jan 14;13(1):230. doi: 10.3390/nu13010230.

Reference Type: RESULT

PMID: 33466826 (View on PubMed)

Cromie KJ, Threapleton DE, Snart CJP, Taylor E, Mason D, Wright B, Kelly B, Reid S, Azad R, Keeble C, Waterman AH, Meadows S, McKillion A, Alwan NA, Cade JE, Simpson NAB, Stewart PM, Zimmermann M, Wright J, Waiblinger D, Mon-Williams M, Hardie LJ, Greenwood DC. Maternal iodine status in a multi-ethnic UK birth cohort: associations with autism spectrum disorder. BMC Pediatr. 2020 Dec 5;20(1):544. doi: 10.1186/s12887-020-02440-y.

Reference Type: RESULT

PMID: 33276760 (View on PubMed)

Provided Documents

Document Type: Statistical Analysis Plan

View Document

Document Type: Informed Consent Form: Born in Bradford cohort Informed Consent Form

View Document

Document Type: Informed Consent Form: Hiba longitudinal cohort Informed Consent Form

View Document

Study Documents

Document Type: Individual Participant Data Set

Submit expressions of interest on a short proforma. All suggestions will be reviewed by the BiB Executive Group.

View Document

Other Identifiers

PR-R10-0514-11004

Identifier Type: -

Identifier Source: org_study_id