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A review of the iodine status of UK pregnant women and its implications for the offspring.

ABSTRACT: Iodine, as a component of the thyroid hormones, is crucial for brain development and is therefore especially important during pregnancy when the brain is developing most rapidly. While randomised controlled trials of pregnant women in regions of severe iodine deficiency have shown that prenatal iodine deficiency causes impaired cognition, less is known of the effects in regions of mild deficiency. This is relevant to the UK as the World Health Organisation now classifies the UK as mildly iodine deficient, based on a national study of 14-15 year old schoolgirls in 2011. We have previously published a study using samples and data from the UK-based Avon Longitudinal Study of Parents and Children (ALSPAC) that found an association between low iodine status in early pregnancy (urinary iodine-to-creatinine ratio <150 ?g/g) and lower verbal IQ and reading scores in the offspring. Though the women in ALSPAC were recruited in the early 1990s, the results of the study are still relevant as their iodine status was similar to that reported in recent studies of UK pregnant women. This review discusses the evidence that mild-to-moderate iodine deficiency during pregnancy has deleterious effects on child neurodevelopment and relates that evidence to the data on iodine status in the UK. It has highlighted a need for nationwide data on iodine status of pregnant women and that a randomised controlled trial of iodine supplementation in pregnant women in a region of mild-to-moderate iodine deficiency with child outcomes as the primary endpoint is required.

SUBMITTER: Bath SC

PROVIDER: S-EPMC4442695 | biostudies-other | 2015 Aug

REPOSITORIES: biostudies-other

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A review of the iodine status of UK pregnant women and its implications for the offspring.

Bath Sarah C SC Rayman Margaret P MP

Environmental geochemistry and health 20150207 4

Iodine, as a component of the thyroid hormones, is crucial for brain development and is therefore especially important during pregnancy when the brain is developing most rapidly. While randomised controlled trials of pregnant women in regions of severe iodine deficiency have shown that prenatal iodine deficiency causes impaired cognition, less is known of the effects in regions of mild deficiency. This is relevant to the UK as the World Health Organisation now classifies the UK as mildly iodine ...[more]

PMID: 25663363

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Project description:Background:Historically, Iceland has been an iodine-sufficient nation due to notably high fish and milk consumption. Recent data suggest that the intake of these important dietary sources of iodine has decreased considerably. Objective:To evaluate the iodine status of pregnant women in Iceland and to determine dietary factors associated with risk for deficiency. Methods:Subjects were women (n = 983; 73% of the eligible sample) attending their first ultrasound appointment in gestational weeks 11-14 in the period October 2017-March 2018. Spot urine samples were collected for assessment of urinary iodine concentration (UIC) and creatinine. The ratio of iodine to creatinine (I/Cr) was calculated. Median UIC was compared with the optimal range of 150-249 ?g/L defined by the World Health Organization (WHO). Diet was assessed using a semiquantitative food frequency questionnaire (FFQ), which provided information on main dietary sources of iodine in the population studied (dairy and fish). Results:The median UIC (95% confidence interval (CI)) and I/Cr of the study population was 89 ?g/L (42, 141) and 100 (94, 108) ?g/g, respectively. UIC increased with higher frequency of dairy intake, ranging from median UIC of 55 (35, 79) ?g/L for women consuming dairy products <1 time per week to 124 (98, 151) ?g/L in the group consuming dairy >2 times per day (P for trend <0.001). A small group of women reporting complete avoidance of fish (n = 18) had UIC of 50 (21, 123) ?g/L and significantly lower I/Cr compared with those who did not report avoidance of fish (58 (34, 134) ?g/g vs. 100 (94, 108) ?g/g, P = 0.041). Women taking supplements containing iodine (n = 34, 3.5%) had significantly higher UIC compared with those who did not take supplements (141 (77, 263) ?g/L vs. 87 (82, 94), P = 0.037). Conclusion:For the first time, insufficient iodine status is being observed in an Icelandic population. There is an urgent need for a public health action aiming at improving iodine status of women of childbearing age in Iceland.

Project description:Background Iodine is one of the crucial micronutrients needed by the human body, and is vitally important during pregnancy. This study aimed to determine the relationship between the iodine status of pregnant women and their knowledge, and practices regarding iodized salt. All participants were enrolled in the Butajira nutrition, mental health and pregnancy (BUNMAP) cohort, Butajira, Ethiopia in February-May, 2019. Methods In this cross-sectional study, 152 pregnant women without hypertension or known thyroid disease before or during pregnancy were randomly selected from the BUNMAP mother to child cohort (n = 832). Spot urine samples were collected to estimate the level of urinary iodine concentration (UIC). Salt samples were also collected from their homes. The Sandall-Kolthoff (S-K) method was used to measure the level of iodine in the urine samples, and iodometric titration was used to measure the level of iodine in the salt. Data was entered and cleaned using Epi-info version 3.5.3 and then exported to SPSS version 20 for further analysis. Multivariate logistic regression analysis was performed to identify associations in the collected data. Results The WHO recommended level of iodine for populations of pregnant women is 150–249 F06Dg/L. The median UIC among pregnant women in this study was 151.2 μg/L [interquartile range (IQR) = 85.5–236.2 F06Dg/L], at the low end of this range. About half (49.65%) of the participants were likely to be iodine deficient. There was a significant association between having a formal job (AOR = 2.56; CI = 1.11–5.96) and iodine sufficiency. Based on a cutoff of >15 ppm (mg/kg), 91.7% (95% CI: 87.2–96.2) of the salts collected from the household had adequate iodine content. The median iodine level of the collected salt samples was 34.9 mg/kg (ppm) (IQR = 24.2–44.6 mg/kg). Conclusions The UNICEF 2018 guidelines for adequate iodine nutrition in pregnant women include both a recommended median range of 150–249 μg/L, and an upper limit of 20% on the fraction of the population with UIC below 50 μg/L. Because our study population’s median level is 151.2 μg/L and the percentage of pregnant women with urinary iodine concentration of less than 50 μg/L is 9.7% (14/145), the women received adequate iodine nutrition. The availability of adequately iodized salt in households is more than 90%, as recommended by WHO. In light of previous iodine deficiency in this region of Ethiopia, the salt iodization program promotes the health of babies and mothers.

Project description:BackgroundIt is a priority to achieve an adequate nutritional status of iodine during pregnancy since iodine deficiency in this population may have repercussions on the mother during both gestation and post partum as well as on the foetus, the neonate and the child at different ages. According to the WHO, iodine deficiency is the most frequent cause of mental retardation and irrreversible cerebral lesions around the world. However, few studies have been published on the nutritional status of iodine in the pregnant population within the Primary Care setting, a health care level which plays an essential role in the education and control of pregnant women. Therefore, the aim of the present study is: 1.- To know the hygiene-dietetic habits related to the intake of foods rich in iodine and smoking during pregnancy. 2.- To determine the prevalence of iodine deficiency and the factors associated with its appearance during pregnancy.Methods/designWe will perform a cluster randomised, controlled, multicentre trial. Randomisation unit: Primary Care Team.Study population898 pregnant women over the age of 17 years attending consultation to a midwife during the first trimester of pregnancy in the participating primary care centres.Outcome measuresconsumption of iodine-rich foods and iodine deficiency. Points of assessment: each trimester of the gestation.Interventiongroup education during the first trimester of gestation on healthy hygiene-dietetic habits and the importance of an adequate iodine nutritional status.Statistical analysisdescriptive analysis of all variables will be performed as well as multilevel logistic regression. All analyses will be done carried out on an intention to treat basis and will be fitted for potential confounding factors and variables of clinical importance.DiscussionEvidence of generalised iodine deficiency during pregnancy could lead to the promotion of interventions of prevention such as how to improve and intensify health care educational programmes for pregnant women.Trial registrationClinicalTrials.gov: NCT01301768.

Project description:Background: Globally, iodine deficiency has been drastically reduced since the introduction of salt iodization programs; nonetheless, many populations remain at-risk for iodine deficiency. This study aimed to assess the iodine status among women of reproductive age in Uzbekistan and to identify factors associated with iodine deficiency, including the availability of adequately iodized salt at the household level. Methods: A cross-sectional household survey was conducted to produce region-specific estimates of the household coverage with adequately iodized salt and iodine status among women for each of the 14 regions in Uzbekistan. Other information, such as socioeconomic status, lactation and pregnancy, residence, age, and consumption of iodine supplements, was also collected. Results: Overall, 36% of 3413 households had adequately iodized salt (iodine concentration >15 ppm [parts per million (mg I/kg salt)]), 20% had inadequately iodized salt (5-14 ppm), and 44% had salt without detectable iodine (<5 ppm). Adequate iodization was found in 33.2% of the 2626 salt samples taken from retail packages labeled as "iodized," 36.5% of the 96 samples taken from retail packages without mention of iodization, and 50.5% of the 674 samples without the original packaging (p < 0.001). The median urinary iodine concentration (UIC) of 140.9 μg/L (95% confidence interval [CI 132.4-150.7]) in nonpregnant nonlactating women indicated adequate iodine status, while for nonpregnant lactating and pregnant women, the median UIC of 112.9 μg/L [CI 99.3-128.4] and 117.3 μg/L [CI 101.8-139.9], respectively, indicated borderline adequacy. Significant differences in UIC (p < 0.001) were found between nonpregnant nonlactating women living in households with adequately iodized salt (UIC 208.9 μg/L), inadequately iodized salt (UIC 139.1 μg/L), and noniodized salt (UIC 89.9 μg/L). Conclusions: Coverage with adequately iodized salt is low in Uzbekistan, and women in households with poorly iodized salt have substantially worse iodine status; claims on packaging about salt iodization do not reflect salt iodine content. This highlights the importance and effectiveness of salt iodization and the need to strengthen this program in Uzbekistan.

Project description:BACKGROUND:Studies indicate that mild to moderate iodine deficiency in pregnancy may have a long-term negative impact on child neurodevelopment. These effects are likely mediated via changes in maternal thyroid function, since iodine is essential for the production of thyroid hormones. However, the impact of iodine availability on thyroid function during pregnancy and on thyroid function reference ranges are understudied. The aim of this study was to investigate the association between iodine intake and thyroid function during pregnancy. DESIGN:In a population-based pregnancy cohort including 2910 pregnant women participating in The Norwegian Mother and Child Cohort Study, we explored cross sectional associations of maternal iodine intake measured (1) by a food frequency questionnaire and (2) as iodine concentration in a spot urine sample, with plasma thyroid hormones and antibodies. RESULTS:Biological samples were collected in mean gestational week 18.5 (standard deviation 1.3) and diet was assessed in gestational week 22. Median iodine intake from food was 121??g/day (interquartile range 90, 160), and 40% reported use of iodine-containing supplements in pregnancy. Median urinary iodine concentration (UIC) was 59??g/L among those who did not use supplements and 98??g/L in the women reporting current use at the time of sampling, indicating mild to moderate iodine deficiency in both groups. Iodine intake as measured by the food frequency questionnaire was not associated with the outcome measures, while UIC was inversely associated with FT3 (p?=?0.002) and FT4 (p?<?0.001). Introduction of an iodine-containing supplement after gestational week 12 was associated with indications of lower thyroid hormone production (lower FT4, p?=?0.027, and nonsignificantly lower FT3, p?=?0.17). The 2.5th and 97.5th percentiles of TSH, FT4, and FT3 were not significantly different by groups defined by calculated iodine intake or by UIC. CONCLUSION:The results indicate that mild to moderate iodine deficiency affect thyroid function in pregnancy. However, the differences were small, suggesting that normal reference ranges can be determined based on data also from mildly iodine deficient populations, but this needs to be further studied. Introducing an iodine-containing supplement might temporarily inhibit thyroid hormone production and/or release.

Dataset Information

A review of the iodine status of UK pregnant women and its implications for the offspring.

Publications

A review of the iodine status of UK pregnant women and its implications for the offspring.

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