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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; 18:132. [PMID: 32522280 PMCID: PMC7288513 DOI: 10.1186/s12916-020-01602-0] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/04/2020] [Accepted: 04/21/2020] [Indexed: 01/02/2023] Open
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.
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Affiliation(s)
- Charles Jonathan Peter Snart
- Leeds Institute of Cardiovascular & Metabolic Medicine, LIGHT Laboratories, School of Medicine, University of Leeds, Leeds, LS2 9JT, UK
| | - Diane Erin Threapleton
- Leeds Institute of Cardiovascular & Metabolic Medicine, LIGHT Laboratories, School of Medicine, University of Leeds, Leeds, LS2 9JT, UK
| | - Claire Keeble
- Leeds Institute for Data Analytics, University of Leeds, Leeds, LS2 9JT, UK
| | - Elizabeth Taylor
- Leeds Institute of Cardiovascular & Metabolic Medicine, LIGHT Laboratories, School of Medicine, University of Leeds, Leeds, LS2 9JT, UK
| | - Dagmar Waiblinger
- Bradford Institute for Health Research, Bradford Teaching Hospitals NHS Foundation Trust, Bradford, BD9 6RJ, UK
| | - Stephen Reid
- Earth Surface Science Institute, School of Earth and Environment, University of Leeds, Leeds, LS2 9JT, UK
| | - Nisreen A Alwan
- School of Primary Care and Population Sciences, Faculty of Medicine, Southampton General Hospital, University of Southampton, Southampton, SO16 6YD, UK.,NIHR Southampton Biomedical Research Centre, University of Southampton and University Hospital Southampton NHS Foundation Trust, Southampton, UK
| | - Dan Mason
- Bradford Institute for Health Research, Bradford Teaching Hospitals NHS Foundation Trust, Bradford, BD9 6RJ, UK
| | - Rafaq Azad
- Bradford Institute for Health Research, Bradford Teaching Hospitals NHS Foundation Trust, Bradford, BD9 6RJ, UK
| | - Janet Elizabeth Cade
- Nutritional Epidemiology Group, School of Food Science & Nutrition, University of Leeds, Leeds, LS2 9JT, UK
| | - Nigel A B Simpson
- Division of Women's and Children's Health, School of Medicine, University of Leeds, Leeds, LS2 9JT, UK
| | - Sarah Meadows
- Elsie Widdowson Laboratory, University of Cambridge, Cambridge, CB1 9NL, UK.,NIHR Nutritional Biomarker Laboratory, MRC Epidemiology Unit, University of Cambridge, Clifford Allbutt Building, Hills Road, Cambridge, CB2 0AH, UK
| | - Amanda McKillion
- Elsie Widdowson Laboratory, University of Cambridge, Cambridge, CB1 9NL, UK.,NIHR Nutritional Biomarker Laboratory, MRC Epidemiology Unit, University of Cambridge, Clifford Allbutt Building, Hills Road, Cambridge, CB2 0AH, UK
| | - Gillian Santorelli
- Bradford Institute for Health Research, Bradford Teaching Hospitals NHS Foundation Trust, Bradford, BD9 6RJ, UK
| | | | - Michael Zimmermann
- Laboratory for Human Nutrition, Institute of Food, Nutrition and Health, ETH Zurich, 8092, Zürich, Switzerland
| | - Paul M Stewart
- Faculty of Medicine and Health, University of Leeds, Leeds, LS2 9JT, UK
| | - John Wright
- Bradford Institute for Health Research, Bradford Teaching Hospitals NHS Foundation Trust, Bradford, BD9 6RJ, UK
| | | | - Darren Charles Greenwood
- Leeds Institute of Cardiovascular & Metabolic Medicine, LIGHT Laboratories, School of Medicine, University of Leeds, Leeds, LS2 9JT, UK. .,Leeds Institute for Data Analytics, University of Leeds, Leeds, LS2 9JT, UK.
| | - Laura J Hardie
- Leeds Institute of Cardiovascular & Metabolic Medicine, LIGHT Laboratories, School of Medicine, University of Leeds, Leeds, LS2 9JT, UK.
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Koukkou E, Ilias I, Mamalis I, Adonakis GG, Markou KB. Serum Thyroglobulin Concentration Is a Weak Marker of Iodine Status in a Pregnant Population with Iodine Deficiency. Eur Thyroid J 2016; 5:120-4. [PMID: 27493886 PMCID: PMC4949369 DOI: 10.1159/000446070] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/22/2015] [Revised: 04/08/2016] [Indexed: 11/19/2022] Open
Abstract
OBJECTIVE To assess the reliability of thyroglobulin (Tg) as a marker of iodine status during pregnancy. DESIGN 299 women aged 30.5 ± 4.8 years (mean ± SD) were studied. METHODS In every subject, we measured urinary iodine concentration (UIC), serum thyrotropin (TSH), Tg, free thyroxine (fT4), Tg autoantibodies (TgAbs) and human chorionic gonadotropin (hCG) levels. We excluded samples with increased TgAbs from the analysis. RESULTS According to WHO criteria, the study population was iodine deficient in every trimester. Serum Tg levels did not differ during the three trimesters of pregnancy. Serum hCG levels fell significantly as pregnancies advanced. A weak, significantly negative correlation (limited to the 3rd trimester) was found between Tg and UIC (ρ = -0.187, p = 0.039). Serum fT4 decreased as pregnancies advanced and TSH increased. Serum fT4 was negatively correlated with TSH (ρ = -0.161, p = 0.006) and positively with hCG (ρ = +0.165, p = 0.005). The multiple regression equation of Tg based on hCG, TSH, UIC and trimester of pregnancy was significant but weak (F = 4.057, p = 0.003; R(2) = 0.055), with hCG as a significant predictor Tg (p for log hCG = 0.041). CONCLUSIONS Tg cannot be considered as a valid marker of iodine deficiency in pregnancy, at least in a mildly iodine-deficient environment. Further studies in a larger patient cohort with differences in iodine status, as well as studies on Tg changes after improving iodine status in pregnant women, are needed in order to corroborate these results.
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Affiliation(s)
- Eftychia Koukkou
- Department of Endocrinology, E Venizelou Maternity Hospital, Athens, Greece
| | - Ioannis Ilias
- Department of Endocrinology, E Venizelou Maternity Hospital, Athens, Greece
| | - Irene Mamalis
- Departments of Endocrinology, University of Patras Medical School, Patras, Greece
| | - Georgios G. Adonakis
- Departments of Obstetrics and Gynecology, University of Patras Medical School, Patras, Greece
| | - Kostas B. Markou
- Departments of Endocrinology, University of Patras Medical School, Patras, Greece
- *Kostas B. Markou, MD, Thisseos Street 6, GR–26500 Ovria Patras (Greece), E-Mail
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Bath SC, Furmidge-Owen VL, Redman CW, Rayman MP. Gestational changes in iodine status in a cohort study of pregnant women from the United Kingdom: season as an effect modifier. Am J Clin Nutr 2015; 101:1180-7. [PMID: 25948667 PMCID: PMC4441812 DOI: 10.3945/ajcn.114.105536] [Citation(s) in RCA: 49] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2014] [Accepted: 03/31/2015] [Indexed: 11/14/2022] Open
Abstract
BACKGROUND Iodine is required throughout pregnancy for thyroid hormone production, which is essential for fetal brain development. Studies of iodine status in pregnant women from the United Kingdom (UK) have focused on early gestation (<16 wk). Data on the effect of advancing gestation on urinary iodine excretion are conflicting, with suggestions of both an increase and a decrease. OBJECTIVES The aims were to evaluate iodine status in a cohort of UK pregnant women and to explore how it changes throughout gestation. DESIGN We used samples and data from 230 UK pregnant women who were recruited to the Selenium in PRegnancy INTervention study. Iodine concentration was measured in spot-urine samples that were collected at ∼12, 20, and 35 wk of gestation; creatinine concentration was also measured to correct for urine dilution. A linear mixed model was used to explore the effect of gestational week on iodine-to-creatinine ratio, with change in season, body mass index, daily milk intake, and maternal age controlled for. RESULTS The median urinary iodine concentration from urine samples collected at all time points (n = 662) was 56.8 μg/L, and the iodine-to-creatinine ratio was 116 μg/g, thus classifying this cohort as mildly-to-moderately iodine deficient. The median iodine-to-creatinine ratios at 12, 20, and 35 wk were 102.5, 120.0, and 126.0 μg/g, respectively. Only 3% of women were taking iodine-containing prenatal supplements. The iodine-to-creatinine ratio increased with advancing gestation, and there was a significant interaction between gestational week and season (P = 0.026). For a 1-wk increase in gestation, the iodine-to-creatinine ratio increased by a factor of 1.05 (95% CI: 1.02, 1.08) in winter and by a factor of 1.04 (95% CI: 1.00, 1.08) in summer. CONCLUSIONS This group of UK pregnant women was mildly-to-moderately iodine deficient at all trimesters, which is of public health concern. The finding that the iodine-to-creatinine ratio increased over the course of gestation may not be generalizable to populations with different iodine status from ours and merits further investigation. This trial was registered at www.isrctn.com as ISRCTN37927591.
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Affiliation(s)
- Sarah C Bath
- From the University of Surrey, Guildford, United Kingdom (SCB, VF-O, and MPR); Danone Nutricia Early Life Nutrition, Trowbridge, United Kingdom (VF-O); and the Nuffield Department of Obstetrics and Gynecology, University of Oxford, Oxford, United Kingdom (CWGR)
| | - Victoria L Furmidge-Owen
- From the University of Surrey, Guildford, United Kingdom (SCB, VF-O, and MPR); Danone Nutricia Early Life Nutrition, Trowbridge, United Kingdom (VF-O); and the Nuffield Department of Obstetrics and Gynecology, University of Oxford, Oxford, United Kingdom (CWGR)
| | - Christopher Wg Redman
- From the University of Surrey, Guildford, United Kingdom (SCB, VF-O, and MPR); Danone Nutricia Early Life Nutrition, Trowbridge, United Kingdom (VF-O); and the Nuffield Department of Obstetrics and Gynecology, University of Oxford, Oxford, United Kingdom (CWGR)
| | - Margaret P Rayman
- From the University of Surrey, Guildford, United Kingdom (SCB, VF-O, and MPR); Danone Nutricia Early Life Nutrition, Trowbridge, United Kingdom (VF-O); and the Nuffield Department of Obstetrics and Gynecology, University of Oxford, Oxford, United Kingdom (CWGR).
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