Iodine supplementation during pregnancy and infant neuropsychological development. INMA Mother and Child Cohort Study

Too Much Too Little: Clarifying the Relationship Between Maternal Iodine Intake and Neurodevelopmental Outcomes

BACKGROUND

In 2009, the Australian government mandated the fortification of bread salt with iodine. In 2010, pregnant and lactating women were also advised to take an iodine-containing supplement. Our assessment of this policy in an iodine-sufficient population showed that children whose mothers were in the highest and lowest quartiles of iodine intake performed more poorly on early childhood tests of cognition and language than those in the second quartile. However, we did not quantify the iodine intake associated with optimal neurodevelopment.

OBJECTIVES

The aim was to establish the iodine intake range in pregnancy associated with optimal child neurodevelopment.

METHODS

A prospective cohort study of pregnant women and their young children (n = 699). Iodine intake was assessed by a validated food frequency questionnaire at 16 and 28 wk of gestation. Child neurodevelopment at 18 mo of age was measured using the Bayley Scales of Infant and Toddler Development, Third Edition (Bayley-III). The relationship between average iodine intake during pregnancy and child neurodevelopment was assessed using linear regression with fractional polynomials and adjustment for confounders.

RESULTS

Mean (SD) iodine intake was similar at study entry and 28 wk, 308 (120) μg/d, with 82% of women taking iodine supplements at study entry. The relationship between iodine intake during pregnancy and Bayley-III cognitive and language scores was curvilinear (P = 0.001 and P = 0.004, respectively), with the lowest Bayley-III scores observed at lower and higher iodine intakes. The inflection point that drove the association between lower iodine intake in pregnancy and poorer child neurodevelopment scores was around 185 μg/d; for the higher pregnancy iodine intakes, language and cognitive scores were negatively affected from ∼350 μg/d to 370 μg/d, respectively. Higher iodine intakes were being driven by supplement use.

CONCLUSIONS

Targeted, not blanket, iodine supplementation may be needed for pregnant women with low-iodine intake from food.

A Cohort Study on the Effects of Maternal High Serum Iodine Status During Pregnancy on Infants in Terms of Iodine Status and Intellectual, Motor, and Physical Development

The objective of the present study was to explore the effects of maternal iodine excess during pregnancy on infants' neurodevelopment and physical development. A total of 143 mother-child pairs were enrolled in this cohort study. Maternal blood samples were collected during the obstetric examination. A mother-child questionnaire survey was conducted, and infants' blood samples were collected during the newborn physical examination. Infants' single-spot urine samples were collected, and intellectual, motor, and physical development were assessed at 2 months of age. The median (IQR) maternal serum iodine concentrations (SICs) in the first, second, and third trimesters of pregnancy were 91.2 (74.4, 102.2) μg/L, 81.2 (70.6, 94.8) μg/L, and 82.0 (68.9, 100.3) μg/L, respectively. In the first trimester of pregnancy, infants' psychomotor developmental index (PDI), body mass index (BMI) and weight-for-length Z score (WLZ) were higher with maternal suitable SIC (40 ~ 92 μg/L) than with maternal excess SIC (P < 0.05). Infants' PDI, BMI, weight-for-age Z score (WAZ) and WLZ were negatively correlated with maternal SIC (P < 0.05). Maternal excess SIC had a slightly negative effect on infants' MDI (OR = 1.304, P = 0.035, 95% CI = 1.019 ~ 1.668), PDI (OR = 1.124, P = 0.001, 95% CI = 1.052 ~ 1.200) and BMI (OR = 0.790, P = 0.005, 95% CI = 0.669 ~ 0.933). In the third trimester, infants' length-for-age Z score (LAZ) was higher with maternal high SIC (> 92 μg/L) (P = 0.015), and maternal SIC was positively correlated with infants' urine iodine concentration (UIC) (P = 0.026). Maternal iodine excess in the first trimester had a slightly negative effect on infants' intellectual, motor, and physical development. In the third trimester, maternal iodine excess only may have a positive impact on infants' height. Additionally, maternal iodine status was closely related to infants' iodine status.

Maternal Urinary Iodine Concentration during Pregnancy and Its Impact on Child Growth and Neurodevelopment: An 11-Year Follow-Up Study

Mild-to-moderate iodine deficiency during pregnancy is prevalent worldwide, but its consequences for maternal and child health are not clear. We aimed to investigate the impact of maternal iodine intake during pregnancy on the child's growth and neurodevelopment. This study involved a cohort of 11-year-old children (n = 70) whose mothers had participated in an iodine intake survey during pregnancy. Gestational, neonatal, anthropometric, intelligence quotient (IQ), and socioeconomic parameters were analyzed according to maternal urinary iodine concentration (UIC). There was a positive linear trend of current height Z-score, full-scale IQ, verbal IQ, family income, maternal education, and a negative trend of neonatal TSH levels with increasing maternal UIC levels. However, regression analysis indicated that maternal UIC was not an independent predictor of any gestational, neonatal, or childhood development parameter. Only maternal school education was positively associated with child height and IQ. In conclusion, we did not find any evidence of a direct effect of maternal iodine intake during pregnancy on the long-term growth and neurodevelopment of children. The results suggest that socioeconomic factors are important confounding factors that affect both maternal iodine intake and child development and must be considered when investigating the association between maternal iodine intake and child outcomes.

Prenatal iodine supplementation and early childhood neurodevelopment: the PoppiE trial - study protocol for a multicentre randomised controlled trial

INTRODUCTION

Observational studies suggest both low and high iodine intakes in pregnancy are associated with poorer neurodevelopmental outcomes in children. This raises concern that current universal iodine supplement recommendations for pregnant women in populations considered to be iodine sufficient may negatively impact child neurodevelopment. We aim to determine the effect of reducing iodine intake from supplements for women who have adequate iodine intake from food on the cognitive development of children at 24 months of age.

METHODS AND ANALYSIS

A multicentre, randomised, controlled, clinician, researcher and participant blinded trial with two parallel groups. Using a hybrid decentralised clinical trial model, 754 women (377 per group) less than 13 weeks' gestation with an iodine intake of ≥165 µg/day from food will be randomised to receive either a low iodine (20 µg/day) multivitamin and mineral supplement or an identical supplement containing 200) µg/day (amount commonly used in prenatal supplements in Australia), from enrolment until delivery. The primary outcome is the developmental quotient of infants at 24 months of age assessed with the Cognitive Scale of the Bayley Scales of Infant Development, fourth edition. Secondary outcomes include infant language and motor development; behavioural and emotional development; maternal and infant clinical outcomes and health service utilisation of children. Cognitive scores will be compared between groups using linear regression, with adjustment for location of enrolment and the treatment effect described as a mean difference with 95% CI.

ETHICS AND DISSEMINATION

Ethical approval has been granted from the Women's and Children's Health Network Research Ethics Committee (HREC/17/WCHN/187). The results of this trial will be presented at scientific conferences and published in peer-reviewed journals.

TRIAL REGISTRATION NUMBER

NCT04586348.

Iodine status during child development and hearing ability: a systematic review

Iodine, through the thyroid hormones, is required for the development of the auditory cortex and cochlea (the sensory organ for hearing). Deafness is a well-documented feature of endemic cretinism resulting from severe iodine deficiency. However, the range of effects of suboptimal iodine intake during auditory development on the hearing ability of children is less clear. We therefore aimed to systematically review the evidence for the association between iodine exposure (i.e. intake/status/supplementation) during development (i.e. pregnancy and/or childhood) and hearing outcomes in children. We searched PubMed and Embase and identified 330 studies, of which thirteen were included in this review. Only three of the thirteen studies were of low risk of bias or of good quality, this therefore limited our ability to draw firm conclusions. Nine of the studies (69 %) were in children (one RCT, two non-RCT interventions and six cross-sectional studies) and four (31 %) were in pregnant women (one RCT, one cohort study and two case reports). The RCT of iodine supplementation in mildly iodine-deficient pregnant women found no effect on offspring hearing thresholds. However, hearing was a secondary outcome of the trial and not all women were from an iodine-deficient area. Iodine supplementation of severely iodine-deficient children (in both non-RCT interventions) resulted in improved hearing thresholds. Five of six cross-sectional studies (83 %) found that higher iodine status in children was associated with better hearing. The current evidence base for the association between iodine status and hearing outcomes is limited and further good-quality research on this topic is needed.

Iodine Status Modifies the Association between Fluoride Exposure in Pregnancy and Preschool Boys' Intelligence

In animal studies, the combination of in utero fluoride exposure and low iodine has greater negative effects on offspring learning and memory than either alone, but this has not been studied in children. We evaluated whether the maternal urinary iodine concentration (MUIC) modifies the association between maternal urinary fluoride (MUF) and boys' and girls' intelligence. We used data from 366 mother-child dyads in the Maternal-Infant Research on Environmental Chemicals Study. We corrected trimester-specific MUF and MUIC for creatinine, and averaged them to yield our exposure variables (MUFCRE, mg/g; MUICCRE, µg/g). We assessed children's full-scale intelligence (FSIQ) at 3 to 4 years. Using multiple linear regression, we estimated a three-way interaction between MUFCRE, MUICCRE, and child sex on FSIQ, controlling for covariates. The MUICCRE by MUFCRE interaction was significant for boys (p = 0.042), but not girls (p = 0.190). For boys whose mothers had low iodine, a 0.5 mg/g increase in MUFCRE was associated with a 4.65-point lower FSIQ score (95% CI: -7.67, -1.62). For boys whose mothers had adequate iodine, a 0.5 mg/g increase in MUFCRE was associated with a 2.95-point lower FSIQ score (95% CI: -4.77, -1.13). These results suggest adequate iodine intake during pregnancy may minimize fluoride's neurotoxicity in boys.

Gestational and childhood urinary iodine concentrations and children's cognitive function in a longitudinal mother-child cohort in rural Bangladesh

BACKGROUND

Severe iodine deficiency adversely affects neurodevelopment; however, evidence regarding the association of non-severe deficiency and child cognitive functioning is inconclusive.

METHODS

This prospective mother-child cohort study was nested in a population-based nutritional supplementation trial in Bangladesh (Maternal and Infant Nutrition Interventions in Matlab [MINIMat]). Participants with data on cognitive abilities at 5 and 10 years of age (n = 1530) and at least one measurement of urinary iodine concentration (UIC) (gestational week 8, 5, and 10 years) were selected. Cognitive abilities were assessed using the Wechsler Preschool and Primary Scale of Intelligence (WPPSI-III) and Wechsler Intelligence Scale for Children (WISC-IV). UICs were measured with inductively coupled plasma mass spectrometry and thereafter adjusted for specific gravity.

RESULTS

Median UICs in our population: (282 μg/L [pregnancy]; 406 μg/L [5 years]; 294 μg/L [10 years]) indicated that iodine intake corresponded to above 'adequate' or even 'excessive', according to the WHO classification. Maternal 'UIC <150 μg/L' was associated with lower full-scale and verbal scores at 5 and 10 years, although the associations were weakened in the fully adjusted models. A tendency of decreased verbal scores was also observed for maternal 'UIC ≥500 μg/L' but not for the corresponding child iodine category (≥300 μg/L). Child 'UIC <100 μg/L' was associated with lower processing speed (B=-3.1, 95% CI [-6.2, -0.1]; P-value = 0.041) compared with the reference group (100 μg/L≤ UIC <300 μg/L).

CONCLUSIONS

Current findings add to the growing evidence of a causal association of early-life iodine intake with cognitive development, indicating that low iodine intake during childhood is associated with reduced processing speed and non-optimal gestational iodine intake is weakly associated with slightly poorer verbal development outcomes.

A Meta-Analysis of the Effect of Iodine Excess on the Intellectual Development of Children in Areas with High Iodine Levels in their Drinking Water

The purpose of this meta-analysis is to comprehensively investigate the effect of iodine excess on children's intellectual development in areas with high iodine levels in their drinking water. We systematically searched the electronic databases and identified 17 publications (16 in Chinese and 1 in English) on the effect of iodine excess on children's intelligence published between January 31, 1985, and January 31, 2020. This meta-analysis included 14,794 children from 28 studies. The results showed that compared with the control group, the intelligence level of children in the high iodine group reduced significantly by 1.64 points (WMD=-1.64; 95% CI (-3.225, -0.049), Z=2.02, P<0.05). Subgroup analyses were performed according to the water iodine concentration, water iodine concentration of the control group, the intelligence test method, and regions of China (i.e., north and south). We noted that when the water iodine concentration was <300μg/L, 301-600μg/L, 600.1-900μg/L, and >900μg/L, the intelligence level of the high iodine groups decreased by varying degrees, although not statistically significant (all P>0.05). The water iodine concentration of the control group was divided into two groups (<150 μg/L and <100 μg/L) and the heterogeneity analysis showed that the heterogeneity of the control group decreased significantly when the concentration of water iodine was <150 μg/L, I² = 67.3%, P<0.001, which indicated a potential source of heterogeneity. The analyses by test method showed that among the studies which used the China Joint Raven's test, the intelligence level of children in the high iodine group was 0.86 points lower than in the control group (P>0.05). Conversely, we observed that among the studies which used the China Binet intelligence test and the binaphthalene intelligence test of Tanzhida in Japan to evaluate children's intelligence level, the intelligence level of children in the high iodine groups was significantly lower (3.65 points and 8.0 points, respectively) compared with the control groups (P<0.05). The analysis of the regions of China demonstrated that whereas the reduction in children's intelligence level from excess iodine in the north of China was not statistically significant (WMD=-0.16, 95% CI (-2.18, 1.85), P>0.05), the association was statistically significant in the southern part of China (WMD=-1.86, 95% CI (-3.57, -0.09), P<0.05). This study found that high iodine concentration was statistically significantly associated with a decline in intelligence level in children. Comparatively, the intelligence level of children who were exposed to high iodine concentrations reduced significantly by 1.64 points. These findings have public health implications.

OUP accepted manuscript

Context

Adequate iodine intake is essential throughout life. Key dietary sources are iodized salt and animal products, but dietary patterns in Europe are changing, for example toward lower salt intake and a more plant-based diet.

Objective

To review iodine intake (not status) in European populations (adults, children, and pregnant women) to identify at-risk groups and dietary sources.

Data sources

PubMed, Embase, and Cochrane databases, as well as European national nutrition surveys were searched for data on had iodine intake (from dietary assessment) and sources of iodine, collected after 2006.

Data selection

In total, 57 studies were included, comprising 22 national surveys and 35 sub-national studies. Iodine intake data were available from national surveys of children aged <10 years (n = 11), 11–17 years (n = 12), and adults (n = 15), but data from pregnancy were only available from sub-national studies.

Results

Iodine intake data are lacking—only 17 of 45 (38%) European countries had iodine-intake data from national surveys. Iodine intake reported from national surveys was below recommendations for: (1) children aged <10 years in 2 surveys (18%), (2) boys and girls aged 11–17 years in 6 (50%) and 8 (68%) surveys, respectively, and (3) adult men and women in 7 (47%) and 12 (80%) surveys, respectively. In pregnant women, intake was below recommendations except where women were taking iodine-containing supplements. Just 32% of national surveys (n = 7) included iodized salt when estimating iodine intake. Milk, dairy products, fish, and eggs were important contributors to intake in many countries, suggesting limited sources in plant-based diets.

Conclusion

Results are limited by the challenges of dietary assessment for measuring iodine intake. Future national surveys should include iodine intake. Policy makers should consider dietary sources alongside any iodized salt policies when considering methods for improving population iodine intake.

Systematic Review Registration

PROSPERO 2017 CRD42017075422.

Iodine supplementation for pregnant women: a cross-sectional national interventional study

BACKGROUND

Although Iran has been considered iodine replete since 2000, the first national survey of iodine intake among Iranian pregnant women in 2014 indicated that despite the adequate intake of iodine by the general population, this vulnerable group has moderate iodine deficiency. Therefore, in this national cross-sectional interventional study, we aimed to assess the iodine intake and thyroid function of Iranian pregnant women 2 years after implementing national iodine supplementation for this vulnerable group.

MATERIALS AND METHODS

In this cross-sectional study, we conducted a national interventional survey of pregnant women. A total of 1200 pregnant women (400 women from each trimester) from 12 provinces of Iran were recruited from the antenatal care clinics from October 2018 to March 2019. The median urinary iodine concentration (MUIC), as an indicator of iodine status in three spot urine samples, was measured, along with the serum total T4 (TT4), thyrotropin (TSH), thyroglobulin (Tg), thyroid peroxidase antibody (TPO-Ab), and iodine content of household salt.

RESULTS

The mean age of the cohort was 28 ± 6.2 years, with the mean gestational age of 22.7 ± 13.0 weeks. The overall MUIC (IQR) of pregnant women was 188 µg/L (124.2-263 µg/L). Also, the MUICs in the three trimesters of pregnancy were 174 µg/L (110-254), 175 µg/L (116-251), and 165 µg/L (114-235), respectively. The MUICs ≥ 150, 100-149, and < 100 µg/L were found in 63, 19.8, and 16.2% of the subjects, respectively. The mean TT4 level was 12 ± 4.5 µg/dL, and the median (IQR) level of TSH was 2.37 mIU/L (1.66-3.18 mIU/L). According to our local reference range, 118 (10.5%) pregnant women had subclinical hypothyroidism, 6 (0.53%) women had isolated hypothyroxinemia, and 65 (5.7%) women were TPO-Ab positive. Also, the median (IQR) level of Tg was 10.08 µg/dL (5.7-20.4 µg/dL), and the median iodine content of household salt was 29.6 µg/g; the iodine content was ≥ 30 µg/g in 85% of household salt. The results showed that more than 95% of households were under iodized salt coverage.

CONCLUSION

The results of this study indicated that iodine supplementation with at least 150 µg of iodine per day improved the iodine intake of pregnant women. Except for subclinical hypothyroidism, the prevalence of clinical hypothyroidism, clinical/subclinical thyrotoxicosis, TPO-Ab positivity, and isolated hypothyroxinemia decreased significantly, which emphasizes the importance of iodine supplementation during pregnancy.

Effect of iodine supplementation in pregnancy on neurocognitive development on offspring in iodine deficiency areas: a systematic review

Objective

To investigate the effect of iodine supplementation during gestation on the neurocognitive development of children in areas where iodine deficiency is common.

Methods

Based on the PRISMA methodology, we conducted the search for articles in the PubMed, LILACS and Scopus databases, between March and April 2020, without limitation of dates. We used descriptors in English, Portuguese, and Spanish, without filters. Four clinical trials and four cohort articles were included in the review.

Results

The maximum supplementation was 300 μg of potassium iodide per day. The Bayley scale and Children's Communication Checklist-Short were used to assess neurodevelopment in children. There was no significant improvement in the children's mental development index and behavioural development index in the supplemented group; however, the psychomotor development index (PDI) showed improvement in the poorer gross motor skills. We found differences in the response time to sound in the supplemented group living in mild deficiency areas.

Conclusion

Daily supplementation with iodine can improve poor psychomotor development of children living in mild to moderate iodine deficiency areas. Thus, it is necessary to perform further studies to assess the effect of supplementation on neurodevelopment before, during and after gestation in mild to moderate iodine deficiency areas.

Urinary Iodine Concentrations in Pregnant Women and Offspring Brain Morphology

Background: Severe maternal iodine deficiency during pregnancy leads to marked intellectual disability in the offspring. Although recent studies showed that even mild-to-moderate maternal iodine deficiency is associated with lower intelligence quotient and attention deficit hyperactivity disorder in offspring, the underlying neurobiological mechanism of these associations remains unknown. The aim of this study was to investigate the association of maternal iodine excretion during pregnancy with offspring brain morphology during pre-adolescence. Methods: This study was embedded within Generation R, a prospective population-based birth cohort in Rotterdam, the Netherlands. We included 990 mother-child pairs with data on urinary iodine concentration (UIC) and creatinine during pregnancy. The UIC was assessed at <18 and/or 18-25 weeks of gestation and offspring brain imaging data were acquired with magnetic resonance imaging (MRI) at age 10 years. We used linear regression to study the association of the iodine-to-creatinine ratio (UI/Creat) with offspring brain MRI outcomes. Results: Maternal UI/Creat during pregnancy was not consistently associated with offspring brain morphology. A low UI/Creat (<150 μg/g) during pregnancy was nominally associated with smaller total gray matter volume, but this did not survive correction for multiple testing. Also, we could not identify a linear association between continuous iodine excretion and offspring brain morphology. Instead, our results suggest a curvilinear association between UI/Creat and brain morphology. In sensitivity analyses using the World Health Organization categorization for UIC values, both low and high UI/Creat were associated with smaller total gray matter volume. Conclusions: The current study provides some but no conclusive evidence for an association of maternal iodine excretion during pregnancy with offspring brain morphology. Our results suggest that the exact definition of the reference group is important because of potential non-linear associations, which could be leveraged in future studies.

Nutritional Iodine Status in Pregnant Women from Health Area IV in Asturias (Spain): Iodised Salt Is Enough

Background: Iodine deficiency during pregnancy may have adverse effects on the neurodevelopment of the foetus. Recent studies of pregnant women in Asturias (Spain) indicate that nutritional iodine levels are sufficient. The objective of this study was to confirm the appropriate nutritional iodine status and to analyse the influence of the ingestion of iodine on maternal urinary iodine concentration (UIC) and thyroid function. Methods: An observational study was carried out between May and June 2017 on women in the first trimester of pregnancy from Health Area IV in Asturias. The women completed a questionnaire related to their consumption of iodine and samples were taken to analyse UIC and thyroid function. Results: Three hundred and eighteen pregnant women were involved. Of these, 51.10% used iodised salt, 48.90% consumed ≥ 2 servings of dairy products daily and 87.08% took iodine supplements. The median UIC was 171.5 μg/L (116–265 μg/L) and 60.41% of women had UIC ≥ 150 μg/L. Multivariate logistic regression analysis demonstrated that iodised salt had a protective effect on UIC < 150 μg/L (odds ratio (OR) 0.404 (0.237–0.683), p = 0.001), but not iodine supplements (OR 0.512 (0.240–1.085), p = 0.080). The average level of thyroid stimulating hormone (TSH) was 2.26 ± 0.94 mIU/L; 68.40% of pregnant women taking iodine supplements had TSH < 2.5 mIU/L compared to 30.00% of those who were not taking supplements (p = 0.031). Conclusions: The pregnant women in our health area are maintaining appropriate nutritional iodine levels. The consumption of iodised salt protects against iodine deficiency; thus, iodine supplements should be taken on an individualised basis.

Iron, iodine and vitamin D deficiencies during pregnancy: epidemiology, risk factors and developmental impacts

Micronutrient deficiency persists throughout the world, and although the burden is higher in low-resource settings, it is also prevalent in wealthy countries, a phenomenon termed 'hidden hunger'. Due to their high requirements for vitamins and minerals relative to their energy intake, young women and children are particularly vulnerable to hidden hunger. As they share several risk factors and impact on overlapping outcomes, we consider how deficiency of iron, iodine and vitamin D can have profound impacts on perinatal health and infant development. We review the epidemiology of these micronutrient deficiencies during pregnancy, including social, environmental and dietary risk factors. We identify the main challenges in defining nutritional status of these nutrients using validated diagnostic criteria linked with meaningful clinical outcomes. Public health strategies are urgently required to improve the overall health and nutritional status of women of reproductive age. Obesity prevention and early detection of malnutrition with standardised screening methods would detect pregnant women at increased risk of iron deficiency. Development of sensitive, individual biomarkers of iodine status is required to protect maternal health and fetal/infant brain development. Risk assessments of vitamin D requirements during pregnancy need to be revisited from the perspective of fetal and neonatal requirements. International consensus on standardised approaches to micronutrient assessment, analysis and reporting as well as sensitive, clinically validated infant and child neuro-behavioural outcomes will enable progression of useful observational and intervention studies.

Iodine status in UK-An accidental public health triumph gone sour

The improvement in iodine status among the UK population from the 1930s onwards has been described as an 'accidental public health triumph' despite the lack of any iodine fortification program. However, iodine deficiency in the UK has re-emerged in vulnerable groups and is likely due to a combination of changing farming practices, dietary preferences and public health priorities. The UK is now among only a minority of European countries with no legislative framework for iodine fortification. The experience of folic acid fortification and the 28-year delay in its implementation lays bare the political difficulties of introducing any fortification program in the UK. If iodine fortification is not an imminent possibility, then it is important to explore other options: how to change farming practice especially on organic farms; encourage dairy intake; protect and expand our public health programs of milk provision for vulnerable groups and embark on education programs for women of childbearing potential and healthcare professionals. This review explores how the UK may have arrived at this juncture and how the iodine status of the nation may be improved at this time of major political and public health upheaval.

A randomized, double-blind study of iodine supplementation during pregnancy in Sweden: pilot evaluation of maternal iodine status and thyroid function

Purpose

Pregnant women in Sweden are mildly iodine deficient. We investigated the effect of daily iodine supplementation on the iodine and thyroid status of pregnant women.

Methods

In this pilot, randomized, double-blind trial, 200 thyroid-healthy pregnant women were recruited at mean (standard deviation) pregnancy week 8.85 (1.62) and assigned (1:1) to daily intake of a multivitamin tablet with or without 150 μg of iodine. Urine and serum samples were collected at baseline and once during the second and third trimesters. Urinary iodine concentration (UIC), serum thyroglobulin (Tg), thyroid-stimulating hormone (TSH), free thyroxine (FT4), and thyroid peroxidase antibodies (TPOabs) were analyzed. Neonatal TSH data were collected. UIC and Tg were also analyzed in a group of 89 thyroid-healthy non-pregnant women of reproductive age (WRA).

Results

At baseline, the intervention and the control groups had similar median UIC (interquartile range (IQR)): 110 μg/L (74–119) and 111 μg/L (66–168), respectively. The intervention group reached iodine sufficiency with median UIC (IQR) 139 μg/L (89–234) and 136 μg/L (91–211) in the second and third trimester, respectively, without significant difference from the lower limit of the recommended range, i.e. 150–250 μg/L (p = 0.42 and p = 0.87, respectively). The intervention group had higher median UIC and lower median Tg compared to the control group during the second (p < 0.001 and p = 0.019, respectively) and third trimester (p < 0.001 and p = 0.003, respectively), whereas thyroid hormones, serum TPOabs, and neonatal TSH were similar. The WRA group presented median UIC (IQR) 65 μg/L (30–98) and median Tg (IQR) 18 μg/L (13–27).

Conclusion

A daily supplement containing 150 μg of iodine to a group of pregnant women with mild iodine deficiency improved the iodine status from mild ID to iodine sufficiency. This improvement seems to have had a positive impact on maternal thyroglobulin. This study is now under extension to investigate the children’s neuropsychological development.

Trial registration

ClinicalTrials.gov Identifier NCT02378246, May 3, 2015, retrospectively registered.

Effects of Two Weekly Servings of Cod for 16 Weeks in Pregnancy on Maternal Iodine Status and Infant Neurodevelopment: Mommy's Food, a Randomized-Controlled Trial

Background: Mild-to-moderate iodine deficiency is still present in many countries, particularly in pregnant women. Observational studies suggest that mild-to-moderate iodine deficiency during pregnancy may be associated with impaired thyroid function and child neurodevelopment. Randomized-controlled food trials to increase iodine status are scarce. We assessed the impact of an increased intake of cod during pregnancy on maternal iodine status and infant neurodevelopment. Methods: In this randomized-controlled trial, pregnant women in Bergen, Norway, recruited through Haukeland University Hospital, were randomly assigned (1:1) to an intervention of 200 g of cod twice a week for 16 weeks (gestational week 20-36) or to continue with their standard diet (control group). Randomization was done by lottery. Primary outcome was urinary iodine concentration (UIC) (spot samples from six consecutive days) measured postintervention. Secondary outcome was infant neurodevelopment assessed by the cognitive, language, and motor scales of the Bayley Scales of Infant and Toddler Developmental third edition (Bayley-III) at 11 months of age. In addition, maternal thyroid function was measured (thyrotropin [TSH], free triiodothyronine [fT3], free thyroxine [fT4]) at baseline and postintervention. Results: Between January 2016 until February 2017, 137 women were recruited. Postintervention UIC was higher in the intervention group (n = 61) [median (interquartile range, IQR) 98 (64-145) μg/L], compared with control (n = 61) [median (IQR) 73 (52-120) μg/L] (p = 0.028), also after adjusting for baseline UIC (p = 0.048). Infants of mothers in the intervention group had a lower cognitive composite score on the Bayley-III compared with the control group (p = 0.045). There were no group differences in the Bayley III language- or motor composite scores. Maternal thyroid hormones (TSH, fT3, fT4) did not differ between the groups postintervention. Conclusions: Increased cod intake during pregnancy improved the iodine status in women with mild-to-moderate iodine deficiency, however, did not affect thyroid function. The negative effect on cognition should be followed up to assess whether this is a stable effect over time. More studies are warranted to enable good health advice on iodine nutrition in pregnancy. ClinicalTrials.gov NCT02610959. Registered November 20, 2015.

Iodine and fertility: do we know enough?

Iodine is a vital micronutrient and its importance in thyroid function is well established. However, abnormalities in iodine intake may also have other effects. In particular, iodine is taken up avidly by the ovary and endometrium. Iodine deficiency is associated with reduced fertility. The use of high iodine concentration contrast media has recently been shown to improve conception rates in couples with unexplained infertility (UI). We hypothesize that this improvement could be related to the iodine excess and mechanisms independent of its action on thyroid. In this article, the metabolism of iodine and its potential role in fertility will be discussed, including the impact of both iodine deficiency and excess states and the importance of iodine in normal fetal development. This will include insights from animal studies on the effect of iodine in the uterine and ovarian structural environment, hormonal milieu and immunological factors affecting implantation. We speculate that iodine may well have a role as a potential therapy for UI.

Safety and efficacy of supplements in pregnancy

Pregnancy is a time where expectant mothers often focus on their diet to improve their own health and to preserve the future health of their children. There is much conflicting information in the public domain about the safety and/or efficacy of nutritional supplements during pregnancy. Despite this, the market for supplements is growing. This review discusses the roles of critical nutrients in pregnancy and the available evidence on the use of supplements to reduce risks and improve maternal and fetal outcomes. Recommendations are made for pregnant women, taking into account safety data and tolerable upper intakes set for pregnant women. It is important for dieticians, nutritionists, physicians, and other healthcare providers to be able to offer accurate and evidence-based advice on supplement use in pregnancy. Routine supplementation may not be necessary for all, but individuals at risk are identified.

Systematic review and meta-analysis of the effects of iodine supplementation on thyroid function and child neurodevelopment in mildly-to-moderately iodine-deficient pregnant women

BACKGROUND

Mild-to-moderate iodine deficiency, particularly in pregnancy, is prevalent; this is of concern because observational studies have shown negative associations with child neurodevelopment. Although neither the benefits nor the safety of iodine supplementation in pregnancy in areas of mild-to-moderate deficiency are well researched, such supplementation is increasingly being recommended by health authorities in a number of countries.

OBJECTIVES

By reviewing the most recent published data on the effects of iodine supplementation in mildly-to-moderately deficient pregnant women on maternal and infant thyroid function and child cognition, we aimed to determine whether the evidence was sufficient to support recommendations in these areas.

METHODS

A systematic review of randomized controlled trials (RCTs), non-RCT interventions, and observational studies was conducted. To identify relevant articles, we searched the PubMed and Embase databases. We defined mild-to-moderate iodine deficiency as a baseline median urinary iodine concentration (UIC) of 50-149 µg/L. Eligible studies were included in meta-analyses.

RESULTS

In total, 37 publications were included-10 RCTs, 4 non-RCT interventions, and 23 observational studies. Most studies showed no effect of iodine supplementation on maternal or infant thyroid-stimulating hormone and free thyroxine. Most RCTs found that supplementation reduced maternal thyroglobulin and in 3 RCTs, it prevented or diminished the increase in maternal thyroid volume during pregnancy. Three RCTs addressed child neurodevelopment; only 1 was adequately powered. Meta-analyses of 2 RCTs showed no effect on child cognitive [mean difference (MD): -0.18; 95% CI: -1.22, 0.87], language (MD: 1.28; 95% CI: -0.28, 2.83), or motor scores (MD: 0.28; 95% CI: -1.10, 1.66).

CONCLUSIONS

There is insufficient good-quality evidence to support current recommendations for iodine supplementation in pregnancy in areas of mild-to-moderate deficiency. Well-designed RCTs, with child cognitive outcomes, are needed in pregnant women who are moderately deficient (median UIC < 100 µg/L). Maternal intrathyroidal iodine stores should be considered in future trials by including appropriate measures of preconceptional iodine intake.This review was registered at www.crd.york.ac.uk/prospero as CRD42018100277.

Iodine status and supplementation before, during, and after pregnancy

Iodine intake is essential for the production of thyroid hormone. Iodine deficiency remains a public health problem in many regions around the world. Iodine deficiency can present as a spectrum of disorders depending on the degree of severity. Pregnant and lactating women are particularly vulnerable to iodine deficiency disorders because of their increased iodine requirements. Severe maternal iodine deficiency has been associated with cretinism or impaired neurodevelopment in children as well as obstetric complications. Universal salt iodization has been shown to prevent these disorders in severely iodine deficient areas. Recently, observational studies have demonstrated an association between mild-to-moderate iodine deficiency and poorer cognitive outcomes in children. In this review, we describe the iodine requirements for pregnant and lactating women, how population iodine status can be assessed, the effects of maternal iodine deficiency and excess, and current data regarding efficacy of iodine supplementation for women who are pregnant or lactating.

Iodine nutrition in pregnant and breastfeeding women: sufficiency, deficiency, and supplementation

Iodine is a micronutrient used by the thyroid gland to produce thyroid hormones, which manage different aspects of body metabolism. Humans depend on exogenous sources of iodine to maintain the normal concentration of thyroid hormones. Pregnancy alters iodine turnover and is associated with significant changes in thyroid function. Daily iodine requirement during pregnancy increases to 250 μg, compared with 150 μg for nonpregnant women. According to recent guidelines of scientific organizations, to improve maternal thyroid status and to prevent child neurocognitive defects, all pregnant and breastfeeding women should take 150 μg of iodine supplementation, not only in iodine-deficient regions but also in iodine-sufficient areas. However, some recent studies have confirmed that iodine supplementation of mildly iodine-deficient pregnant women has no clear benefits as concerns maternal thyroid function or child neurodevelopment.

Maternal Iodine Status During Pregnancy Is Not Consistently Associated with Attention-Deficit Hyperactivity Disorder or Autistic Traits in Children

BACKGROUND

Severe iodine deficiency during pregnancy can cause intellectual disability, presumably through inadequate placental transfer of maternal thyroid hormone to the fetus. The association between mild-to-moderate iodine deficiency and child neurodevelopmental problems is not well understood.

OBJECTIVES

We investigated the association of maternal iodine status during pregnancy with child attention-deficit hyperactivity disorder (ADHD) and autistic traits.

METHODS

This was a collaborative study of 3 population-based birth cohorts: Generation R (n = 1634), INfancia y Medio Ambiente (n = 1293), and the Avon Longitudinal Study of Parents and Children (n = 2619). Exclusion criteria were multiple fetuses, fertility treatment, thyroid-interfering medication use, and pre-existing thyroid disease. The mean age of assessment in the cohorts was between 4.4 and 7.7 y for ADHD symptoms and 4.5 and 7.6 y for autistic traits. We studied the association of the urinary iodine-to-creatinine ratio (UI/Creat) <150 μg/g-in all mother-child pairs, and in those with a urinary-iodine measurement at ≤18 weeks and ≤14 weeks of gestation-with the risk of ADHD or a high autistic-trait score (≥93rd percentile cutoff), using logistic regression. The cohort-specific effect estimates were combined by random-effects meta-analyses. We also investigated whether UI/Creat modified the associations of maternal free thyroxine (FT4) or thyroid-stimulating hormone concentrations with ADHD or autistic traits.

RESULTS

UI/Creat <150 μg/g was not associated with ADHD (OR: 1.2; 95% CI: 0.7, 2.2; P = 0.56) or with a high autistic-trait score (OR: 0.8; 95% CI: 0.6, 1.1; P = 0.22). UI/Creat <150 μg/g in early pregnancy (i.e., ≤18 weeks or ≤14 weeks of gestation) was not associated with a higher risk of behavioral problems. The association between a higher FT4 and a greater risk of ADHD (OR: 1.3; 95% CI: 1.0, 1.6; P = 0.017) was not modified by iodine status.

CONCLUSIONS

There is no consistent evidence to support an association of mild-to-moderate iodine deficiency during pregnancy with child ADHD or autistic traits.

Iodine Deficiency and Supplementation in Pregnancy

Iodine deficiency during pregnancy is an important global public health issue and the leading preventable cause of neurodevelopmental impairments worldwide. The effects of severe iodine deficiency during pregnancy, including adverse obstetric outcomes and decreased child intelligence quotient, have been clearly established. However, the effects of mild-to-moderate deficiency remain less well understood. Pregnant and lactating women have higher iodine requirements than other adults; intakes of 220 to 250 µg/d in pregnancy and 250 to 290 µg/d in lactation. In this article, we describe iodine metabolism, iodine requirements in pregnancy and lactation, the effects of both iodine deficiency and excessive iodine intakes in pregnancy, and the efficacy of iodine supplementation.

Iodine Supplementation in Mildly Iodine-Deficient Pregnant Women Does Not Improve Maternal Thyroid Function or Child Development: A Secondary Analysis of a Randomized Controlled Trial

Background: Iodine deficiency during pregnancy may be associated with lower offspring IQ, but there are few data on the safety and efficacy of maternal iodine supplementation on child development. In a previously reported multi-center randomized trial conducted in Thailand and India, we assessed the effect of iodine supplementation in mildly iodine-deficient pregnant women on offspring development. In this secondary analysis of that trial, we report data only from the Thai pregnant women in the study, who were more iodine deficient at entry. Methods: Pregnant women in Bangkok, Thailand, were randomized to receive daily 200 μg oral iodine or placebo until delivery. We assessed thyroid size and thyroid function during pregnancy and cognitive and motor development at ages 1, 2, and 5.7 years. The trial was registered at www.clinicaltrials.gov/NCT00791466. Findings: Women (n = 514) entered the trial between November 2008 and March 2011 at a mean ± SD gestational age of 11 ± 2.8 weeks; their median (IQR) UIC was 112 (75, 170) μg/L. Mean compliance with supplementation was 88%. We assessed 397 mothers in the 3rd trimester, 231 infants at age 2 y, and 157 children at mean age 5.7 y. During pregnancy, there was a slightly greater decrease in free and total thyroxine concentrations in the iodine group (p < 0.05). At age 2 years, the iodine group had borderline lower scores for combined fine and gross motor function (p = 0.05), but there were no other significant differences in development. At 5.7 years, there were no significant group differences in child development. Conclusion: Daily iodine supplementation in mildly iodine deficient pregnant women was associated with small negative effects on maternal thyroxine concentrations, but did not affect child development. The safety and efficacy of iodine supplementation in mildly-iodine deficient pregnant women needs to be evaluated further in large randomized controlled trials.

Association of Maternal Iodine Status With Child IQ: A Meta-Analysis of Individual Participant Data

CONTEXT

Although the consequences of severe iodine deficiency are beyond doubt, the effects of mild to moderate iodine deficiency in pregnancy on child neurodevelopment are less well established.

OBJECTIVE

To study the association between maternal iodine status during pregnancy and child IQ and identify vulnerable time windows of exposure to suboptimal iodine availability.

DESIGN

Meta-analysis of individual participant data from three prospective population-based birth cohorts: Generation R (Netherlands), INMA (Spain), and ALSPAC (United Kingdom); pregnant women were enrolled between 2002 and 2006, 2003 and 2008, and 1990 and 1992, respectively.

SETTING

General community.

PARTICIPANTS

6180 mother-child pairs with measures of urinary iodine and creatinine concentrations in pregnancy and child IQ. Exclusion criteria were multiple pregnancies, fertility treatment, medication affecting the thyroid, and preexisting thyroid disease.

MAIN OUTCOME MEASURE

Child nonverbal and verbal IQ assessed at 1.5 to 8 years of age.

RESULTS

There was a positive curvilinear association of urinary iodine/creatinine ratio (UI/Creat) with mean verbal IQ only. UI/Creat <150 µg/g was not associated with lower nonverbal IQ (-0.6 point; 95% CI: -1.7 to 0.4 points; P = 0.246) or lower verbal IQ (-0.6 point; 95% CI: -1.3 to 0.1 points; P = 0.082). Stratified analyses showed that the association of UI/Creat with verbal IQ was only present up to 14 weeks of gestation.

CONCLUSIONS

Fetal brain development is vulnerable to mild to moderate iodine deficiency, particularly in the first trimester. Our results show that potential randomized controlled trials investigating the effect of iodine supplementation in women with mild to moderate iodine deficiency on child neurodevelopment should begin supplementation not later than the first trimester.

Systemic endocrinopathies (thyroid conditions and diabetes): impact on postnatal life of the offspring

Fetal programming may influence childhood and adult life, determining the risk of specific diseases. During earlier stages of pregnancy, the transfer of maternal thyroid hormones to the fetus is vital for adequate neurologic development. The presence of severe maternal thyroid dysfunction, particularly severe iodine deficiency, is devastating, leading to irreversible neurologic sequelae. Moreover, mild maternal thyroid conditions, such as a mild-to-moderate iodine deficiency, may also lead to milder neurologic and behavioral conditions later during the life of the offspring. Maternal dysglycemia due to pregestational or gestational diabetes mellitus is another common situation in which fetal development encounters a hostile environment. Hyperglycemia in utero may trigger metabolic conditions in the offspring, including abnormalities of glucose tolerance and weight excess. Physicians assisting pregnant women have to be aware about these conditions, because they may go unnoticed if not properly screened. Because an early diagnosis and appropriate management may prevent most of the possible negative consequences for the progeny, the prevention, early diagnosis, and proper management of these endocrine conditions should be offered to all women undergoing pregnancy. Here, we comprehensively review the current evidence about the effects of maternal thyroid dysfunction and maternal dysglycemia on the cognitive function and carbohydrate metabolism in the offspring, two prevalent conditions of utmost importance for the child's health and development.

Iodine deficiency in pregnant women in Sweden: a national cross-sectional study

Purpose

Voluntary salt iodization at 50 mg/kg salt ensures adequate iodine nutrition in Swedish school-aged children, but iodine status in pregnant women is uncertain.

Methods

We conducted a cross-sectional national study of 743 pregnant women, at median gestational age of 23 weeks (IQR 9, 38), recruited from maternal health care centers. We measured: urinary iodine concentration (UIC) and urinary creatinine concentration in spot urine samples; thyroglobulin (Tg), thyroid-stimulating hormone (TSH), and total thyroxine (tT4) on dried blood spots (DBS); and thyreoperoxidase antibodies in serum samples. Data on dietary supplement use were obtained, and women were classified as supplement users (consuming multivitamins containing ≥ 150 µg iodine/day) and non-supplement users (no supplements or < 150 µg iodine/day from supplements).

Results

Overall median UIC [bootstrapped 95% confidence interval (CI)] was 101 µg/L (95, 108; n = 737): 149 µg/L (132, 164) in supplement users (n = 253) and 85 µg/L (79, 92) in non-supplement users (n = 440) (p < 0.001). Overall geometric mean DBS-Tg (95% CI) was 22.1 μg/L (20.8, 23.5; n = 675) and the prevalence of elevated DBS-Tg was 19%. DBS-Tg was lower in supplement users (n = 229) than in non-supplement users (n = 405) (19.1 vs 24.4 μg/L, p < 0.001). DBS-TSH, DBS-tT4, and S-TPOab positivity did not differ between the two groups.

Conclusions

Pregnant women in Sweden have inadequate iodine nutrition. Women not taking iodine supplements containing ≥ 150 µg iodine/day are affected by mild iodine deficiency and are at higher risk for increased thyroid activity, while maintaining euthyroidism. Iodine intake should be improved in women both before and after conception by promotion of iodized salt instead of non-iodized salt. We urge regular monitoring of iodine status in the general Swedish population, as well as in risk groups.

Optimal Assessment and Quantification of Iodine Nutrition in Pregnancy and Lactation: Laboratory and Clinical Methods, Controversies and Future Directions

Iodine intake must be boosted during pregnancy to meet the demands for increased production and placental transfer of thyroid hormone essential for optimal foetal development. Failure to meet this challenge results in irreversible brain damage, manifested in severity from neurological cretinism to minor or subtle deficits of intelligence and behavioural disorders. Attention is now being focused on explaining observational studies of an association between insufficient iodine intake during pregnancy and mild degrees of intellectual impairment in the offspring and confirming a cause and effect relationship with impaired maternal thyroid function. The current qualitative categorisation of iodine deficiency into mild, moderate and severe by the measurement of the median urinary iodine concentration (MUIC) in a population of school-age children, as a proxy measure of dietary iodine intake, is inappropriate for defining the degree or severity of gestational iodine deficiency and needs to be replaced. This review examines progress in analytical techniques for the measurement of urinary iodine concentration and the application of this technology to epidemiological studies of iodine deficiency with a focus on gestational iodine deficiency. We recommend that more precise definitions and measurements of gestational iodine deficiency, beyond a spot UIC, need to be developed. We review the evidence for hypothyroxinaemia as the cause of intrauterine foetal brain damage in gestational iodine deficiency and discuss the many unanswered questions, from which we propose that further clinical studies need to be designed to address the pathogenesis of neurodevelopmental impairments in the foetus and infant. Agreement on the testing instruments and standardization of processes and procedures for Intelligence Quotient (IQ) and psychomotor tests needs to be reached by investigators, so that valid comparisons can be made among studies of gestational iodine deficiency and neurocognitive outcomes. Finally, the timing, safety and the efficacy of prophylactic iodine supplementation for pregnant and lactating women needs to be established and confirmation that excess intake of iodine during pregnancy is to be avoided.

Association Between Maternal Iodine Intake in Pregnancy and Childhood Neurodevelopment at Age 18 Months

There are limited and inconsistent data suggesting that mild iodine deficiency in pregnancy might be associated with poorer developmental outcomes in children. Between 2011 and 2015, we conducted a prospective cohort study in Australia examining the relationship between maternal iodine intake in pregnancy and childhood neurodevelopment, assessed using Bayley Scales of Infant and Toddler Development, Third Edition (Bayley-III), in 699 children at 18 months. Maternal iodine intake and urinary iodine concentration (UIC) were assessed at study entry (<20 weeks' gestation) and at 28 weeks' gestation. Maternal iodine intake in the lowest (<220 μg/day) or highest (≥391 μg/day) quartile was associated with lower cognitive, language, and motor scores (mean differences ranged from 2.4 (95% confidence interval (CI): 0.01, 4.8) to 7.0 (95% CI: 2.8, 11.1) points lower) and higher odds (odds ratios ranged from 2.7 (95% CI: 1.3, 5.6) to 2.8 (95% CI: 1.3, 5.7)) of cognitive developmental delay (Bayley-III score <1 SD) compared with mothers with an iodine intake in the middle quartiles. There was no association between UIC in pregnancy and Bayley-III outcomes regardless of whether UIC and the outcomes were analyzed as continuous or categorical variables. Both low and high iodine intakes in pregnancy were associated with poorer childhood neurodevelopment in this iodine-sufficient population.

The effect of iodine deficiency during pregnancy on child development

It is well known that severe iodine deficiency during pregnancy may cause impaired brain development in the child, with effects on cognitive and motor function, hearing and speech. Whether mild-to-moderate deficiency also affects neurological development is less well known, but in the past decade a number of observational studies have been conducted to answer this question and these studies are reviewed in this article. The picture is now emerging that even mild-to-moderate iodine deficiency during pregnancy may be associated with subtle impairments in cognition and school performance, although the evidence from randomised controlled trials is still lacking. As global efforts to eradicate iodine deficiency in populations continue, it is more likely that mild-to-moderate, rather than severe, iodine deficiency will be the issue of concern in pregnancy, and therefore further research in regions of mild-to-moderate deficiency is required to strengthen the research base and to inform public-health policy.

Contemporary challenges to iodine status and nutrition: the role of foods, dietary recommendations, fortification and supplementation

Iodine deficiency (ID) in women of childbearing age remains a global public health concern, mainly through its impact on fetal and infant neurodevelopment. While iodine status is improving globally, ID is still prevalent in pregnancy, when requirements increase. More than 120 countries have implemented salt iodisation and food fortification, strategies that have been partially successful. Supplementation during pregnancy is recommended in some countries and supported by the WHO when mandatory salt iodisation is not present. The UK is listed as one of the ten countries with the lowest iodine status globally, with approximately 60 % of pregnant women not meeting the WHO recommended intake. Without mandatory iodine fortification or recommendation for supplementation in pregnancy, the UK population depends on dietary sources of iodine. Both women and healthcare professionals have low knowledge and awareness of iodine, its sources or its role for health. Dairy and seafood products are the richest sources of iodine and their consumption is essential to support adequate iodine status. Increasing iodine through the diet might be possible if iodine-rich foods get repositioned in the diet, as they now contribute towards only about 13 % of the average energy intake of adult women. This review examines the use of iodine-rich foods in parallel with other public health strategies, to increase iodine intake and highlights the rare opportunity in the UK for randomised trials, due to the lack of mandatory fortification programmes.

Role of iodine-containing multivitamins during pregnancy for children's brain function: protocol of an ongoing randomised controlled trial: the SWIDDICH study

INTRODUCTION

Iodine is essential for normal brain development. Moderate and severe fetal iodine deficiency results in substantial to serious developmental delay in children. Mild iodine deficiency in pregnancy is associated with neurodevelopmental deficits in the offspring, but evidence from randomised trials is lacking. The aim of the Swedish Iodine in Pregnancy and Development in Children study is to determine the effect of daily supplementation with 150 µg iodine during pregnancy on the offspring's neuropsychological development up to 14 years of age.

METHODS AND ANALYSIS

Thyroid healthy pregnant women (n=1275: age range 18-40 years) at ≤12 weeks gestation will be randomly assigned to receive multivitamin supplements containing 150 µg iodine or non-iodine-containing multivitamin daily throughout pregnancy. As a primary outcome, IQ will be measured in the offspring at 7 years (Wechsler Intelligence Scale for Children-V). As secondary outcomes, IQ will be measured at 3.5 and 14 years, psychomotor development at 18 months and 7 years, and behaviour at 3.5, 7 and 14 years. Iodine status (urinary iodine concentration) will be measured during pregnancy and in the offspring at 3.5, 7 and 14 years. Thyroid function (thyroid hormones, thyroglobulin), and deiodinase type 2 polymorphisms will be measured during pregnancy and in the offspring at 7 and 14 years. Structural MRI or other relevant structural or functional brain imaging procedures will be performed in a subgroup of children at 7 and 14 years. Background and socioeconomic information will be collected at all follow-up times.

ETHICS AND DISSEMINATION

This study is approved by the Ethics Committee in Göteborg, Sweden (Diary numbers: 431-12 approved 18 June 2012 (pregnancy part) and 1089-16 approved 8 February 2017 (children follow-up)). According to Swedish regulations, dietary supplements are governed by the National Food Agency and not by the Medical Product Agency. Therefore, there is no requirement for a monitoring committee and the National Food Agency does not perform any audits of trial conduct. The trial will be conducted in accordance with the Declaration of Helsinki. The participating sites will be contacted regarding important protocol changes, both orally and in writing, and the trial registry database will be updated accordingly. Study results will be presented at relevant conferences, and submitted to peer-reviewed journals with open access in the fields of endocrinology, paediatrics and nutrition. After the appropriate embargo period, the results will be communicated to participants, healthcare professionals at the maternal healthcare centres, the public and other relevant groups, such as the national guideline group for thyroid and pregnancy and the National Food Agency.

TRIAL REGISTRATION NUMBER

NCT02378246; Pre-results.

Iodine intake from supplements and diet during pregnancy and child cognitive and motor development: the INMA Mother and Child Cohort Study

Background

The effect of mild-to-moderate maternal iodine deficiency on the neuropsychological development of their offspring is uncertain. We aimed to assess the association between iodine status during pregnancy and the cognitive and motor development of children at 4–5 years.

Methods

We conducted a prospective cohort study in four Spanish regions with recruitment of pregnant women between 2003 and 2008 and follow-up of their children up to 4–5 years (mean (SD)=4.8 (0.6)). Cognitive and motor function was assessed in 1803 children using the McCarthy Scales of Children’s Abilities. Dietary iodine and supplementation were measured through questionnaires twice during pregnancy. Urinary iodine concentration (UIC) was measured in spot samples. The residuals of a regression of UIC against creatinine were used to define a variable corrected for creatinine (UIC~Cr).

Results

Neither iodine supplements nor iodised salt consumption or maternal UIC were associated with cognitive or motor function. After adjusting for creatinine, children of women with UIC~Cr <100 µg/L had 3.93 (95% CI −6.18 to –1.69) general cognitive scores lower than the reference (150–249 µg/L). Dietary iodine was inversely associated with motor scores and milk but not other dairy products or seafood consumption accounted for this association (beta: −1.36; 95% CI −2.12 to –0.61; per one daily milk serving).

Conclusions

We found an association between low maternal urinary iodine and lower cognitive scores in childhood, although only when corrected for creatinine, adding to the evidence that iodine deficiency may have potential harmful effects on neurodevelopment. Iodine supplementation does not appear to improve child’s neurodevelopment at 4–5 years.

Effect of iodine supplementation in pregnant women on child neurodevelopment: a randomised, double-blind, placebo-controlled trial

BACKGROUND

Iodine deficiency during pregnancy might be associated with reduced intelligence quotient (IQ) score in offspring. We assessed the effect of iodine supplementation in mildly iodine-deficient pregnant women on neurodevelopment of their offspring in areas where schoolchildren were iodine sufficient.

METHODS

In this randomised, placebo-controlled trial, pregnant women in Bangalore, India, and Bangkok, Thailand, were randomly assigned (1:1) to receive 200 μg iodine orally once a day or placebo until delivery. Randomisation was done with a computer-generated sequence and stratified by site. Co-primary outcomes were verbal and performance IQ scores on the Wechsler Preschool and Primary Scale of Intelligence Third Edition (WPPSI-III) and the global executive composite score from the Behaviour Rating Inventory of Executive Function-Preschool Version (BRIEF-P) in the children at age 5-6 years. The trial was double-blinded; some unmasking took place at age 2 years for an interim analysis, but participants and nearly all investigators remained masked to group assignment until age 5-6 years. Analysis was by intention to treat using mixed-effects models. This trial is registered with ClinicalTrials.gov, number NCT00791466.

FINDINGS

Between Nov 18, 2008, and March 12, 2011, 832 women entered the trial at a mean gestational age of 10·7 weeks (SD 2·7); median urinary iodine concentration was 131 μg/L (IQR 81-213). Mean compliance with supplementation was 87%, assessed by monthly tablet counts. 313 children (iodine group, n=159; placebo group, n=154) were analysed for verbal and performance IQ with WPPSI-III and 315 (iodine group, n=159; placebo group, n=156) for overall executive function with BRIEF-P. Mean WPPSI-III scores for verbal IQ were 89·5 (SD 9·8) in the iodine group and 90·2 (9·8) in the placebo group (difference -0·7, 95% CI -2·9 to 1·5; p=0·77), and for performance IQ were 97·5 (12·5) in the iodine group and 99·1 (13·4) in the placebo group (difference -1·6, -4·5 to 1·3; p=0·44). The mean BRIEF-P global executive composite score was 90·6 (26·2) in the iodine group and 91·5 (27·0) in the placebo group (difference -0·9, -6·8 to 5·0; p=0·74). The frequency of adverse events did not differ between groups during gestation or at delivery: 24 women in the iodine group and 28 in the placebo group reported adverse events (iodine group: abortion, n=20; blighted ovum, and n=2; intrauterine death, n=2; placebo group: abortion, n=22; blighted ovum, n=1; intrauterine death, n=2; early neonatal death, n=1; and neonatal death, n=2).

INTERPRETATION

Daily iodine supplementation in mildly iodine-deficient pregnant women had no effect on child neurodevelopment at age 5-6 years.

FUNDING

Swiss National Science Foundation, Nestlé Foundation, Wageningen University and Research, and ETH Zurich.

Nutrition (Micronutrients) in Child Growth and Development: A Systematic Review on Current Evidence, Recommendations and Opportunities for Further Research

OBJECTIVE

An important aspect of malnutrition is deficiency of different micronutrients during pregnancy or early childhood. We systematically reviewed the role of nutrition in child growth (weight or height gain) and development.

METHODS

A comprehensive literature search was done on PubMed/Cochrane Library browsing through 38,795 abstracts until December 31, 2016 to select systematic reviews/meta-analyses and individual randomized controlled trials (RCTs) of micronutrient supplementation.

RESULTS

Micronutrients studied included iron, iodine, folate, zinc, calcium, magnesium, selenium, vitamin D, vitamin A, vitamin B complex, and multiple micronutrients. We summarize evidence with details and results of RCTs, highlight strengths/weaknesses, and critically interpret findings. Effects of breastfeeding-promotion, food-supplementation (complementary and school feeding), conditional-cash-transfers, and integrated nutrition/psychosocial interventions are discussed.

CONCLUSION

Based on this evidence we make policy and programmatic recommendations for supplementation to mothers and children at high-risk of deficiency.

Iodine supplementation for women during the preconception, pregnancy and postpartum period

BACKGROUND

Iodine is an essential nutrient required for the biosynthesis of thyroid hormones, which are responsible for regulating growth, development and metabolism. Iodine requirements increase substantially during pregnancy and breastfeeding. If requirements are not met during these periods, the production of thyroid hormones may decrease and be inadequate for maternal, fetal and infant needs. The provision of iodine supplements may help meet the increased iodine needs during pregnancy and the postpartum period and prevent or correct iodine deficiency and its consequences.

OBJECTIVES

To assess the benefits and harms of supplementation with iodine, alone or in combination with other vitamins and minerals, for women in the preconceptional, pregnancy or postpartum period on their and their children's outcomes.

SEARCH METHODS

We searched Cochrane Pregnancy and Childbirth's Trials Register (14 November 2016), and the WHO International Clinical Trials Registry Platform (ICTRP) (17 November 2016), contacted experts in the field and searched the reference lists of retrieved studies and other relevant papers.

SELECTION CRITERIA

Randomized and quasi-randomized controlled trials with randomisation at either the individual or cluster level comparing injected or oral iodine supplementation (such as tablets, capsules, drops) during preconception, pregnancy or the postpartum period irrespective of iodine compound, dose, frequency or duration.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed trial eligibility, risk of bias, extracted data and conducted checks for accuracy. We used the GRADE approach to assess the quality of the evidence for primary outcomes.We anticipated high heterogeneity among trials, and we pooled trial results using random-effects models and were cautious in our interpretation of the pooled results.

MAIN RESULTS

We included 14 studies and excluded 48 studies. We identified five ongoing or unpublished studies and two studies are awaiting classification. Eleven trials involving over 2700 women contributed data for the comparisons in this review (in three trials, the primary or secondary outcomes were not reported). Maternal primary outcomesIodine supplementation decreased the likelihood of the adverse effect of postpartum hyperthyroidism by 68% (average risk ratio (RR) 0.32; 95% confidence interval (CI) 0.11 to 0.91, three trials in mild to moderate iodine deficiency settings, 543 women, no statistical heterogeneity, low-quality evidence) and increased the likelihood of the adverse effect of digestive intolerance in pregnancy by 15 times (average RR 15.33; 95% CI 2.07 to 113.70, one trial in a mild-deficiency setting, 76 women, very low-quality evidence).There were no clear differences between groups for hypothyroidism in pregnancy or postpartum (pregnancy: average RR 1.90; 95% CI 0.57 to 6.38, one trial, 365 women, low-quality evidence, and postpartum: average RR 0.44; 95% CI 0.06 to 3.42, three trials, 540 women, no statistical heterogeneity, low-quality evidence), preterm birth (average RR 0.71; 95% CI 0.30 to 1.66, two trials, 376 women, statistical heterogeneity, low-quality evidence) or the maternal adverse effects of elevated thyroid peroxidase antibodies (TPO-ab) in pregnancy or postpartum (average RR 0.95; 95% CI 0.44 to 2.07, one trial, 359 women, low-quality evidence, average RR 1.01; 95% CI 0.78 to 1.30, three trials, 397 women, no statistical heterogeneity, low-quality evidence), or hyperthyroidism in pregnancy (average RR 1.90; 95% CI 0.57 to 6.38, one trial, 365 women, low-quality evidence). All of the trials contributing data to these outcomes took place in settings with mild to moderate iodine deficiency. Infant/child primary outcomesCompared with those who did not receive iodine, those who received iodine supplements had a 34% lower likelihood of perinatal mortality, however this difference was not statistically significant (average RR 0.66; 95% CI 0.42 to 1.03, two trials, 457 assessments, low-quality evidence). All of the perinatal deaths occurred in one trial conducted in a severely iodine-deficient setting. There were no clear differences between groups for low birthweight (average RR 0.56; 95% CI 0.26 to 1.23, two trials, 377 infants, no statistical heterogeneity, low-quality evidence), neonatal hypothyroidism/elevated thyroid-stimulating hormone (TSH) (average RR 0.58; 95% CI 0.11 to 3.12, two trials, 260 infants, very low-quality evidence) or the adverse effect of elevated neonatal thyroid peroxidase antibodies (TPO-ab) (average RR 0.61; 95% CI 0.07 to 5.70, one trial, 108 infants, very low-quality evidence). All of the trials contributing data to these outcomes took place in areas with mild to moderate iodine deficiency. No trials reported on hypothyroidism/elevated TSH or any adverse effect beyond the neonatal period.

AUTHORS' CONCLUSIONS

There were insufficient data to reach any meaningful conclusions on the benefits and harms of routine iodine supplementation in women before, during or after pregnancy. The available evidence suggested that iodine supplementation decreases the likelihood of postpartum hyperthyroidism and increases the likelihood of the adverse effect of digestive intolerance in pregnancy - both considered potential adverse effects. We considered evidence for these outcomes low or very low quality, however, because of study design limitations and wide confidence intervals. In addition, due to the small number of trials and included women in our meta-analyses, these findings must be interpreted with caution. There were no clear effects on other important maternal or child outcomes though these findings must also be interpreted cautiously due to limited data and low-quality trials. Additionally, almost all of the evidence came from settings with mild or moderate iodine deficiency and therefore may not be applicable to settings with severe deficiency.More high-quality randomised controlled trials are needed on iodine supplementation before, during and after pregnancy on maternal and infant/child outcomes. However, it may be unethical to compare iodine to placebo or no treatment in severe deficiency settings. Trials may also be unfeasible in settings where pregnant and lactating women commonly take prenatal supplements with iodine. Information is needed on optimal timing of initiation as well as supplementation regimen and dose. Future trials should consider the outcomes in this review and follow children beyond the neonatal period. Future trials should employ adequate sample sizes, assess potential adverse effects (including the nature and extent of digestive intolerance), and be reported in a way that allows assessment of risk of bias, full data extraction and analysis by the subgroups specified in this review.

2017 Guidelines of the American Thyroid Association for the Diagnosis and Management of Thyroid Disease During Pregnancy and the Postpartum

BACKGROUND

Thyroid disease in pregnancy is a common clinical problem. Since the guidelines for the management of these disorders by the American Thyroid Association (ATA) were first published in 2011, significant clinical and scientific advances have occurred in the field. The aim of these guidelines is to inform clinicians, patients, researchers, and health policy makers on published evidence relating to the diagnosis and management of thyroid disease in women during pregnancy, preconception, and the postpartum period.

METHODS

The specific clinical questions addressed in these guidelines were based on prior versions of the guidelines, stakeholder input, and input of task force members. Task force panel members were educated on knowledge synthesis methods, including electronic database searching, review and selection of relevant citations, and critical appraisal of selected studies. Published English language articles were eligible for inclusion. The American College of Physicians Guideline Grading System was used for critical appraisal of evidence and grading strength of recommendations. The guideline task force had complete editorial independence from the ATA. Competing interests of guideline task force members were regularly updated, managed, and communicated to the ATA and task force members.

RESULTS

The revised guidelines for the management of thyroid disease in pregnancy include recommendations regarding the interpretation of thyroid function tests in pregnancy, iodine nutrition, thyroid autoantibodies and pregnancy complications, thyroid considerations in infertile women, hypothyroidism in pregnancy, thyrotoxicosis in pregnancy, thyroid nodules and cancer in pregnant women, fetal and neonatal considerations, thyroid disease and lactation, screening for thyroid dysfunction in pregnancy, and directions for future research.

CONCLUSIONS

We have developed evidence-based recommendations to inform clinical decision-making in the management of thyroid disease in pregnant and postpartum women. While all care must be individualized, such recommendations provide, in our opinion, optimal care paradigms for patients with these disorders.

Maternal urinary metabolic signatures of fetal growth and associated clinical and environmental factors in the INMA study

BACKGROUND

Maternal metabolism during pregnancy is a major determinant of the intra-uterine environment and fetal outcomes. Herein, we characterize the maternal urinary metabolome throughout pregnancy to identify maternal metabolic signatures of fetal growth in two subcohorts and explain potential sources of variation in metabolic profiles based on lifestyle and clinical data.

METHODS

We used ¹H nuclear magnetic resonance (NMR) spectroscopy to characterize maternal urine samples collected in the INMA birth cohort at the first (n = 412 and n = 394, respectively, in Gipuzkoa and Sabadell cohorts) and third trimesters of gestation (n = 417 and 469). Metabolic phenotypes that reflected longitudinal intra- and inter-individual variation were used to predict measures of fetal growth and birth weight.

RESULTS

A metabolic shift between the first and third trimesters of gestation was characterized by ¹H NMR signals arising predominantly from steroid by-products. We identified 10 significant and reproducible metabolic associations in the third trimester with estimated fetal, birth, and placental weight in two independent subcohorts. These included branched-chain amino acids; isoleucine, valine, leucine, alanine and 3 hydroxyisobutyrate (metabolite of valine), which were associated with a significant fetal weight increase at week 34 of up to 2.4 % in Gipuzkoa (P < 0.005) and 1 % in Sabadell (P < 0.05). Other metabolites included pregnancy-related hormone by-products of estrogens and progesterone, and the methyl donor choline. We could explain a total of 48-53 % of the total variance in birth weight of which urine metabolites had an independent predictive power of 12 % adjusting for all other lifestyle/clinical factors. First trimester metabolic phenotypes could not predict reproducibly weight at later stages of development. Physical activity, as well as other modifiable lifestyle/clinical factors, such as coffee consumption, vitamin D intake, and smoking, were identified as potential sources of metabolic variation during pregnancy.

CONCLUSIONS

Significant reproducible maternal urinary metabolic signatures of fetal growth and birth weight are identified for the first time and linked to modifiable lifestyle factors. This novel approach to prenatal screening, combining multiple risk factors, present a great opportunity to personalize pregnancy management and reduce newborn disease risk in later life.

Assessing infant cognitive development after prenatal iodine supplementation

Little information is available on infant behavioral development outcomes of prenatal iodine supplementation in regions of mild to moderate iodine deficiency. Studies performed to date, all of which relied on global developmental assessments, have yielded inconsistent findings with regard to psychomotor development, negative findings with regard to mental development, and no information as to the development of specific cognitive functions. Our review of these studies leads us to suspect that the use of global developmental assessments might partially explain the negative and inconsistent findings. To identify cognitive processes that might be sensitive to prenatal iodine supplementation, we examined the timing of thyroid hormone action on specific brain systems. The development of infant visual attention is sensitive to thyroid hormone during the early prenatal period, when the fetus is entirely dependent on maternal thyroid hormone. For this reason, infant visual attention has the potential to be a sensitive measure of infant outcomes in prenatal iodine supplementation studies. We suggest the assessment of infant visual attention, with follow-up examination of childhood executive functions, as a means of capturing the effects of maternal iodine deficiency and prenatal iodine supplementation on specific cognitive processes. In particular, we propose comparison of infant performance on global developmental tests and specialized tests of visual attention in pilot trials of prenatal iodine supplementation in regions of mild to moderate iodine deficiency. Only by comparing the 2 types of tests side by side will it be possible to establish whether the use of a sensitive measure of infant visual attention will increase the reliability of such supplementation studies. Recognizing that exposure misclassification may also provide a partial explanation for the inconsistent neurodevelopmental outcomes in previous studies, we suggest that urinary iodine concentration or creatinine-corrected iodine excretion be monitored regularly in such trials throughout the prenatal period.

Consequences of iodine deficiency and excess in pregnant women: an overview of current knowns and unknowns

Severe iodine deficiency during development results in maternal and fetal hypothyroidism and associated serious adverse health effects, including cretinism and growth retardation. Universal salt iodization is the first-line strategy for the elimination of severe iodine deficiency. Iodine supplementation is recommended for vulnerable groups in severely iodine-deficient regions where salt iodization is infeasible or insufficient. A recent clinical trial has informed best practices for iodine supplementation of severely iodine-deficient lactating mothers. Because of successful programs of universal salt iodization in formerly severely iodine-deficient regions around the world, public health concern has shifted toward mild to moderate iodine deficiency, which remains prevalent in many regions, especially among pregnant women. Observational studies have shown associations between both mild maternal iodine deficiency and mild maternal thyroid hypofunction and decreased child cognition. Iodine supplementation has been shown to improve indexes of maternal thyroid function, even in marginally iodine-deficient areas. However, no data are yet available from randomized controlled trials in regions of mild to moderate iodine insufficiency on the relation between maternal iodine supplementation and neurobehavioral development in the offspring; thus, the long-term benefits and safety of such supplementation are uncertain. Although it is clear that excessive iodine intake can cause alterations in thyroid function in susceptible individuals, safe upper limits for iodine intake in pregnancy have not been well defined. Well-designed, prospective, randomized controlled trials that examine the effects of iodine supplementation on maternal thyroid function and infant neurobehavioral development in mildly to moderately iodine-deficient pregnant women are urgently needed. In addition, clinical data on the effects of iodine excess in pregnant and lactating women are needed to inform current recommendations for safe upper limits on chronic iodine ingestion in general and on iodine supplementation in particular.

Serum Thyroglobulin Concentration Is a Weak Marker of Iodine Status in a Pregnant Population with Iodine Deficiency

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.

Iodine supplementation in pregnancy - is it time?

Iodine is essential for the synthesis of thyroid hormone and optimal foetal neurological development. Pregnant women living in borderline or moderate-severe iodine deficient areas are at particularly high risk of being iodine deficient, and this may have important clinical consequences, particularly for the neurocognitive development of the offspring. It is a substantial problem and many countries including the United Kingdom are mild-moderately iodine deficient. Although the detrimental effects of severe iodine deficiency are well recognized, the benefits of correcting mild-to-moderate iodine deficiency are unclear due to a lack of randomized controlled trials in this area. However, observational data increasingly indicate that there may be substantial health and economic benefits from correcting iodine deficiency in pregnancy. There is now a growing trend from learned societies that iodine supplementation should be utilized in pregnancy in countries with mild-to-moderate iodine deficiency. The dose of iodine supplement needs to reflect local iodine status and iodization policies and will need careful monitoring at the population level to ensure doses to prevent under/excess dosing which would undermine the potential benefits. National tailored guidance is therefore essential.

Contributions of a Child's Built, Natural, and Social Environments to Their General Cognitive Ability: A Systematic Scoping Review

The etiology of a child’s cognitive ability is complex, with research suggesting that it is not attributed to a single determinant or even a defined period of exposure. Rather, cognitive development is the product of cumulative interactions with the environment, both negative and positive, over the life course. The aim of this systematic scoping review was to collate evidence associated with children’s cognitive health, including inherent factors as well as chemical and non-chemical stressors from the built, natural, and social environments. Three databases were used to identify recent epidemiological studies (2003–2013) that examined exposure factors associated with general cognitive ability in children. Over 100 factors were evaluated from 258 eligible studies. We found that recent literature mainly assessed the hypothesized negative effects of either inherent factors or chemical exposures present in the physical environment. Prenatal growth, sleep health, lead and water pollutants showed consistent negative effects. Of the few studies that examined social stressors, results consistently showed cognitive development to be influenced by both positive and negative social interactions at home, in school or the community. Among behavioral factors related to diet and lifestyle choices of the mother, breastfeeding was the most studied, showing consistent positive associations with cognitive ability. There were mostly inconsistent results for both chemical and non-chemical stressors. The majority of studies utilized traditional exposure assessments, evaluating chemical and non-chemical stressors separately. Collective evidence from a limited number of studies revealed that cumulative exposure assessment that incorporates multiple chemical and non-chemical stressors over the life course may unravel the variability in effect on cognitive development and help explain the inconsistencies across studies. Future research examining the interactions of multiple stressors within a child’s total environment, depicting a more real-world exposure, will aid in understanding the cumulative effects associated with a child’s ability to learn.

The effect of iodine supplementation in pregnancy on early childhood neurodevelopment and clinical outcomes: results of an aborted randomised placebo-controlled trial

BACKGROUND

Concern that mild iodine deficiency in pregnancy may adversely affect neurodevelopment of offspring has led to recommendations for iodine supplementation in the absence of evidence from randomised controlled trials. The primary objective of the study was to investigate the effect of iodine supplementation during pregnancy on childhood neurodevelopment. Secondary outcomes included pregnancy outcomes, maternal thyroid function and general health.

METHODS

Women with a singleton pregnancy of fewer than 20 weeks were randomly assigned to iodine (150 μg/d) or placebo from trial entry to birth. Childhood neurodevelopment was assessed at 18 months by using Bayley Scales of Infant and Toddler Development (Bayley-III). Iodine status and thyroid function were assessed at baseline and at 36 weeks' gestation. Pregnancy outcomes were collected from medical records.

RESULTS

The trial was stopped after 59 women were randomly assigned following withdrawal of support by the funding body. There were no differences in childhood neurodevelopmental scores between the iodine treated and placebo groups. The mean cognitive, language and motor scores on the Bayley-III (iodine versus placebo, respectively) were 99.4 ± 12.2 versus 101.7 ± 8.2 (mean difference (MD) -2.3, 95 % confidence interval (CI) -7.8, 3.2; P = 0.42), 97.2 ± 12.2 versus 97.9 ± 11.5 (MD -0.7, 95 % CI -7.0, 5.6; P = 0.83) and 93.9 ± 10.8 versus 92.4 ± 9.7 (MD 1.4, 95 % CI -4.0, 6.9; P = 0.61), respectively. No differences were identified between groups in any secondary outcomes.

CONCLUSIONS

Iodine supplementation in pregnancy did not result in better childhood neurodevelopment in this small trial. Adequately powered randomised controlled trials are needed to provide conclusive evidence regarding the effect of iodine supplementation in pregnancy.

TRIALS REGISTRATION

The trial was registered with the Australian New Zealand Clinical Trials Registry at http://www.anzctr.org.au . The registration number of this trial is ACTRN12610000411044 . The trial was registered on 21 May 2010.

Costs and benefits of iodine supplementation for pregnant women in a mildly to moderately iodine-deficient population: a modelling analysis

BACKGROUND

Results from previous studies show that the cognitive ability of offspring might be irreversibly damaged as a result of their mother's mild iodine deficiency during pregnancy. A reduced intelligence quotient (IQ) score has broad economic and societal cost implications because intelligence affects wellbeing, income, and education outcomes. Although pregnancy and lactation lead to increased iodine needs, no UK recommendations for iodine supplementation have been issued to pregnant women. We aimed to investigate the cost-effectiveness of iodine supplementation versus no supplementation for pregnant women in a mildly to moderately iodine-deficient population for which a population-based iodine supplementation programme--for example, universal salt iodisation--did not exist.

METHODS

We systematically searched MEDLINE, Embase, EconLit, and NHS EED for economic studies that linked IQ and income published in all languages until Aug 21, 2014. We took clinical data relating to iodine deficiency in pregnant women and the effect on IQ in their children aged 8-9 years from primary research. A decision tree was developed to compare the treatment strategies of iodine supplementation in tablet form with no iodine supplementation for pregnant women in the UK. Analyses were done from a health service perspective (analysis 1; taking direct health service costs into account) and societal perspective (analysis 2; taking education costs and the value of an IQ point itself into account), and presented in terms of cost (in sterling, relevant to 2013) per IQ point gained in the offspring. We made data-supported assumptions to complete these analyses, but used a conservative approach that limited the benefits of iodine supplementation and overestimated its potential harms.

FINDINGS

Our systematic search identified 1361 published articles, of which eight were assessed to calculate the monetary value of an IQ point. A discounted lifetime value of an additional IQ point based on earnings was estimated to be £3297 (study estimates range from £1319 to £11,967) for the offspring cohort. Iodine supplementation was cost saving from both a health service perspective (saving £199 per pregnant woman [sensitivity analysis range -£42 to £229]) and societal perspective (saving £4476 per pregnant woman [sensitivity analysis range £540 to £4495]), with a net gain of 1·22 IQ points in each analysis. Base case results were robust to sensitivity analyses.

INTERPRETATION

Iodine supplementation for pregnant women in the UK is potentially cost saving. This finding also has implications for the 1·88 billion people in the 32 countries with iodine deficiency worldwide. Valuation of IQ points should consider non-earnings benefits--eg, health benefits associated with a higher IQ not germane to earnings.

FUNDING

None.

Neurotoxicant exposure during pregnancy is a confounder for assessment of iodine supplementation on neurodevelopment outcome

CONTEXT

The developing brain is vulnerable to iodine deficiency (ID) and environmental neuro-toxicants.

OBJECTIVES

To assess neurocognitive development of children whose mothers have received (or not) iodine supplementation during pregnancy, in an area of borderline ID, while assessing in utero exposure to environmental neuro-toxicants.

DESIGN/PATIENTS

Among 86 children born from normal euthyroid women who participated in our prospective interventional study on iodine supplementation (150 μg/day) started early in pregnancy, 44 (19 with iodine supplementation, 25 controls) were assessed at two years using the Bayley test. Information on parents' education and habits (smoking), and on child development was recorded. Thyroid tests at each trimester of pregnancy and on cord blood (CB) were available, as well as milk concentrations of selected environmental compounds known for their neurotoxicity, including heavy metals and PCBs.

RESULTS

There was no difference in Bayley tests for children born to mothers with and without iodine supplementation, but sample size was small. Language and Social-Emotional Scales were negatively correlated with TBG at all times tested, while PCB 118 correlated negatively with all Language scales. Among maternal and CB thyroid tests, only CB thyroglobulin, the best marker of iodine status, correlated (negatively) with neurodevelopment scales (Motor and Expressive Language).

CONCLUSIONS

This pilot study suggests that PCB118 has a negative impact on neurocognitive development, possibly mitigating the benefit of iodine supplementation in an area of borderline ID. We propose that exposure to environmental neurotoxicants should be taken into account when designing studies on the benefit of iodine supplementation in pregnancy. The potential interactions between TBG, environmental neurotoxicants and brain development warrant further studies.