The Impact of Thyroid Disorders on Clinical Pregnancy Outcomes in a Real-World Study Setting

Pregnancy outcome in subclinical hypothyroidism with and without thyroid peroxidase antibodies-a prospective cohort study

BACKGROUND

Subclinical hypothyroidism (SCH) in pregnancy is associated with adverse foetomaternal outcomes. The literature is scarce with respect to maternal and perinatal outcomes in women with mild SCH (TSH levels between 2.5-4 mIU/L).

OBJECTIVES

The primary objective of the study was to compare the pregnancy outcome between SCH and euthyroid women. The secondary objectives were to find out the proportion of women with SCH having thyroid peroxidase antibodies (TPOAb) and to see the effect of TPOAb positivity on foetomaternal outcomes.

MATERIALS AND METHODS

A total of 178 pregnant women were recruited in the first trimester, and those with TSH between 0.1 and 2.4 mIU/L were considered as euthyroid and 2.5-4mIU/L were labelled as SCH. Women with SCH underwent testing for TPOAb. All women were followed until delivery, and foetomaternal outcomes were assessed.

RESULTS

Amongst SCH group, there was a significantly higher proportion of overweight and obese women (76/91 (83.51%) vs 59/87 (68%), p = 0.031). The neonatal intensive care unit (NICU) admission was higher with adjusted odds ratio of 3.24 (1.41-7.43) in women with SCH as compared to euthyroid women. Otherwise, there was no difference in foetomaternal outcomes between the two groups. The proportion of gestational diabetes mellitus, intrauterine growth retardation and still birth were higher in SCH women with TPOAb as compared to euthyroid. Amongst SCH women, the proportion of induced labour was lower (aOR:0.27 (0.08-0.93) whereas the proportion of stillbirth and low APGAR scores were higher in TPOAb-positive women with a statistically significant difference and adjusted odds ratio (aOR:20.18 (1.84-220.83)) and (aOR:4.77 (1.06-21.3)), respectively, when compared to TPOAb-negative women.

CONCLUSION

There appears to be no difference in pregnancy outcomes between women with SCH and euthyroid women except higher NICU admission in SCH group. Future multi-centre large prospective studies are required to understand better about the pregnancy outcomes in these women.

Subclinical hypothyroidism in the infertile female population: a guideline

There is controversy regarding whether to treat subtle abnormalities of thyroid function in infertile female patients. This guideline document reviews the risks and benefits of treating subclinical hypothyroidism in female patients with a history of infertility and miscarriage, as well as obstetric and neonatal outcomes in this population.

Influence of thyroid autoimmunity at various clinical stages of hypothyroidism on the risk of miscarriage before 20 weeks of gestation

PURPOSE

We aimed to clarify the influence of thyroid autoantibodies at various clinical stages of hypothyroidism on the risk of pregnancy loss before 20 weeks of gestation.

METHODS

We enrolled 230 pregnant women with a history of recurrent miscarriage. Detailed clinical history, physical examination, and laboratory testing of thyroid function, antithyroid peroxidase (anti-TPO), and antithyroglobulin (anti-TG) were applied among all participants.

RESULTS

Coexisting overt hypothyroidism and positive thyroid autoantibodies quadrupled the risk of miscarriage in women before 20 weeks of gestation (OR 4.04, 95% CI = 2.08-7.96, P < 0.001). Women with subclinical hypothyroidism (OR 1.44, 95% CI = 0.81-2.57, P = 0.132,) or who were euthyroid (OR 1.53, 95% CI = 0.86-2.73, P = 0.094) showed a non-significant risk of miscarriage even with positive thyroid autoantibodies. Thyroid-stimulating hormone (TSH) was positively correlated with the number of miscarriages rather than anti-TPO (P < 0.001 and 0.209, respectively).

CONCLUSION

Coexistence of overt hypothyroidism and thyroid autoimmunity was the only significant driver of pregnancy loss before 20 weeks of gestation.

Exploring the Potential of Olfactory Receptor Circulating RNA Measurement for Preeclampsia Prediction and Its Linkage to Mild Gestational Hypothyroidism

Gestational hypothyroidism may lead to preeclampsia development. However, this pathophysiological is unknown. We expect to find a shared mechanism by comparing hypothyroidism and preeclampsia. From our transcriptome data, we recognized olfactory receptors as that fingerprint. The reduction of taste and smell in hypothyroid patients has been known for a long time. Therefore, we decided to look to the olfactory receptors and aimed to identify genes capable of predicting preeclampsia (PEC). Methods: An Ion Proton Sequencer (Thermo Fisher Scientific, Waltham, MA, USA) was used to construct the transcriptome databases. RStudio with packages Limma v.3.50.0, GEOquery v.2.62.2, and umap v.0.2.8.8 were used to analyze the differentially expressed genes in GSE149440 from the Gene Expression Omnibus (GEO). The 7500 Real-Time PCR System (Applied Biosystems, Foster City, CA, USA) was used for RT-qPCR amplification of OR6X1 and OR4E2. Results: Our transcriptomic datasets analysis revealed 25.08% and 26.75% downregulated olfactory receptor (ORs) in mild nontreated gestational hypothyroidism (GHT) and PEC, respectively. In the GSE149440 GEO dataset, we found OR5H1, OR5T3, OR51A7, OR51B6, OR10J5, OR6C6, and OR2AG2 as predictors of early-onset PEC. We also evaluate two chosen biomarkers' responses to levothyroxine. The RT-qPCR demonstrated a difference in OR6X1 and OR4E2 expression between GHT and healthy pregnancy (p < 0.05). Those genes presented a negative correlation with TSH (r: -0.51, p < 0.05; and r: -0.44, p < 0.05), a strong positive correlation with each other (r: 0.89; p < 0.01) and the levothyroxine-treated group had no difference from the healthy one. We conclude that ORs could be used as biomarkers at the beginning of gestation, and the downregulated ORs found in GHT may be improved with levothyroxine treatment.

Impact of thyroid hormone treatment on maternal pregnancy outcomes in women with subclinical hypothyroidism without TPOAb: a retrospective cross-sectional study

BACKGROUND

Evidence on the impact of thyroid hormone treatment (LT4) on maternal pregnancy outcomes in women with subclinical hypothyroidism (SCH) without thyroid peroxidase antibodies (TPOAb) positivity is scarce.

METHODS

Single centre, cross-sectional study in 1460 women screened for TSH, free T4 and TPOAb at median 13 (11-17) weeks of gestation during the period 2013-2014. Exclusion criteria were twin- and assisted reproduction pregnancies, TPO positivity, overt thyroid dysfunction, and treatment with LT4 before screening. The impact of LT4 on maternal pregnancy outcomes was investigated in a group of 53 women with SCH (TSH > 3.74 mIU/L) in which LT4 was initiated at median 13 (10-22) weeks (treated group). The control group included 18 women with SCH (TSH > 3.74 mIU/L). The prevalence of pregnancy complications in these two groups was compared with that in a euthyroid reference (REF) group of 1389 women (TSH ≤ 3.74 mIU/L).

RESULTS

The prevalence of pre-eclampsia and gestational diabetes (GDM) was higher in the control group vs the REF group (16.7% vs 5.0% and 27.8% vs 18.9%; p = 0.017 and p = 0.016, respectively), but comparable in the treated group vs the REF group (7.6% vs 5.0% and 22.6% vs 18.9%; p = 0.918 and 0.676, respectively). The prevalence of iron-deficiency anaemia was lower in the treated vs the REF group (17.0% vs 32.5%; p = 0.017).

CONCLUSION

Pregnant women with untreated SCH and without TPOAb positivity had a higher prevalence of pre-eclampsia and GDM compared with euthyroid women, while this was not the case in women with treated SCH, even when it was initiated after the first trimester.

Maternal preconception thyroid autoimmunity is associated with neonatal birth weight conceived by PCOS women undergoing their first in vitro fertilization/intracytoplasmic sperm injection

BACKGROUND

Thyroid autoimmunity and polycystic ovary syndrome (PCOS) are the most common endocrinopathies and have close relationships based on common etiology and pathogenesis, including genetic susceptibility, metabolic disorders, hormonal dysregulation, immune response, and inflammatory activation. The co-occurrence of both diseases is associated with adverse reproductive outcomes, but its effect on neonatal outcomes remains largely unknown. We aim to explore the effect of thyroid autoimmunity on neonatal birth weight in PCOS women undergoing IVF/ICSI.

METHODS

This is a retrospective analysis of 486 PCOS women who underwent the first IVF/ICSI cycles and gave birth to 361 singletons and 125 twins during 2018 - 2020 at a reproductive center. The associations between maternal preconception serum thyroid function and autoimmunity indicators and birth weights of the singleton and twin groups were evaluated using generalized linear models (GLMs) and generalized estimate equations (GEEs), respectively. Analyses were further stratified by neonatal sex, maternal age, and maternal preconception BMI to assess the possible interaction effects.

RESULTS

Maternal preconception serum TPOAb had a significant negative association with singleton birth weight (P for trends = 0.03). Compared with women in the first tertile of TPOAb, women in the third tertile had a change in singleton birth weight of - 119.72 g (95% CI: - 222.68 g, - 16.70 g). Maternal preconception serum TPOAb had a significant positive association with twin birth weight (P for trends = 0.01). Compared with women in the first tertile of TPOAb, women in the third tertile had a change in twin birth weight of 138.62 g (95% CI: 33.96 g, 243.30 g). Besides, maternal preconception serum TPOAb had a specific association with increased twin birth weight for female neonates, a specific association with decreased singleton birth weight for PCOS women under 35 years, and a specific association with decreased twin birth weight for overweight PCOS women (all P for interactions < 0.05).

CONCLUSIONS

Maternal preconception thyroid autoimmunity may affect the birth weights of both singleton and twin neonates. Further large cohorts and experimental studies are required to confirm these findings and explore the underlying mechanisms.

Thyroid autoimmunity and pregnancy in euthyroid women

Women with thyroid autoimmunity (TAI), predominately characterized by increased levels of thyroid peroxidase antibody (TPOAb), are at risk for developing pregnancy related complications. In this review, we discuss the importance of TAI during natal and perinatal stages. Before pregnancy, TAI is associated with higher mean serum TSH levels and certain causes of subfertility. During pregnancy, TAI increases the risk of an insufficient response of the thyroid to an increasing strain induced by pregnancy, and consequently (subclinical) hypothyroidism might develop. Euthyroid women with TAI have a higher rate of maternal and foetal complications, but it seems that causality cannot be pinned down to thyroid dysfunction alone. Almost half of the women known with TAI prior to pregnancy will also develop post-partum thyroiditis (PPT). However, any relation between PPT and post-partum depression remains uncertain. More research is required to explain possible associations between TAI and pregnancy morbidities, and studies should focus on a better understanding of TAI as such. Given the many unanswered questions, at present, it is not recommended to screen all (potentially) pregnant women for the presence of TAI.

Association between maternal thyroid function and risk of gestational hypertension and preeclampsia

OBJECTIVES

To investigate the influence of maternal level of thyroid-stimulating hormone (TSH), free triiodothyronine (FT3) and free thyroxine (FT4) one by one or in combination on incidence of gestational hypertension and preeclampsia.

METHODS

The study included pregnant women (n=107) hospitalized in the period from July 1, 2020 to October 10, 2021 at the Department of Pathology of Pregnancy of the University Clinic of Obstetrics and Gynecology, University Clinical Center Sarajevo (UCCS) (Bosnia and Herzegovina), due to hypertensive disorder in pregnancy without symptoms of impaired thyroid function. In all patients fulfilling inclusion criteria TSH, FT3, and FT4 using electrochemiluminescence immunoassay (ECLIA, Roche Diagnostics, Basel, Switzerland) were checked. There were two groups of patients: one with gestational hypertension (G1) and the other with preeclampsia (G2). The programs SPSS for Windows 25.0, SPSS Inc, Chicago, IL, USA and Microsoft Excel 11, Microsoft Corporation, Redmond, WA, USA were used for statistical analysis using nonparametric Mann-Whitney U test because the distribution of the data was not normal. The result was considered statistically significant if p<0.05.

RESULTS

Gestational age at delivery (G2 36.86 ± 3.79 vs. G1 38.94 ± 2.15; p=0.002) and birth weight (G2 2,841.36 ± 1,006.39 vs. G2 3,290.73 ± 745.6; p=0,032) were significantly different between the investigated groups. The difference between the peak systolic (p=0.002), peak diastolic blood pressure (p=0.007), TSH (p=0.044), and FT3 (p=0.045) were statistically significant. Impaired thyroid function was observed more often in G2 than in G1.

CONCLUSIONS

Thyroid function was more often affected adversely in pregnancies complicated with preeclampsia than with gestational hypertension. Based on the results of our study it might be prudent to check thyroid hormones in all asymptomatic pregnancies with preeclampsia or gestational hypertension. These findings need confirmation in larger better designed prospective studies.

Indications for intensive care unit treatment among neonates born to mothers with thyroid disease: A population-based cohort study

INTRODUCTION

Thyroid diseases in pregnancy are relatively common and are associated with adverse pregnancy and perinatal outcomes, increasing a neonate's risk of admission to the neonatal intensive care unit (NICU). The aim of this study was to evaluate the indications for increased risk of NICU admission among the neonates of hypothyroid and hyperthyroid mothers.

MATERIAL AND METHODS

The study data consisted of all singleton deliveries (n = 734 773) between 2004 and 2016 in Finland collected from the Finnish Medical Birth Register. The odds of NICU admission (with 95% confidence intervals) were compared between the neonates of hypothyroid or hyperthyroid mothers and of mothers without any thyroid diseases by specified neonatal characteristics and morbidities using logistic regression analysis. The studied neonatal characteristics were preterm birth (<37+0 gestational weeks), low birthweight (<2500 g), the rate of small- and large-for-gestational age infants, and eight disease-specific neonatal outcomes: asphyxia, respiratory distress syndrome, meconium aspiration syndrome, pneumothorax, cardiovascular problems, infections, jaundice and hypoglycemia.

RESULTS

The most common indications for NICU care were principally the same in the neonates of the mothers with and without thyroid disease: respiratory distress syndrome, infections, preterm birth, low birthweight and neonatal hypoglycemia. The preterm neonates, neonates with low birthweight, and large-for-gestational-age infants had increased odds of NICU admission if their mother had hypothyroidism. Also neonates with cardiovascular problems, jaundice or hypoglycemia associated with maternal diabetes had increased odds of NICU admissions if their mother had hypothyroidism. Further, the preterm neonates, large-for-gestational-age infants, and term infants with jaundice had increased odds of NICU admission if their mother had hyperthyroidism.

CONCLUSIONS

The most common indications for NICU care were similar for the neonates of the mothers with and without thyroid disease. However, the neonates of the mothers with thyroid diseases were more likely to need NICU care. The neonates of the mothers with thyroid diseases had higher odds of NICU treatment in cases of preterm birth, large for gestational age, and hypoglycemia.

Preconception TSH and Adverse Pregnancy Outcomes in China: A Nationwide Prospective Cohort Study

BACKGROUND

The relationship between maternal thyroid function and pregnancy outcomes remains controversial and the safe range of TSH is still unclear in women planning pregnancy.

METHODS

This population-based cohort study enrolled Chinese women who became pregnant in 30 provinces from 2010 to 2012 from the National Free Preconception Checkups Project. The maternal TSH level within 6 months before pregnancy and different pregnancy outcomes were collected and analyzed using restricted cubic spline regression model for dose-response relationship and potential optimal cutoff values. Logistic regression was used to reveal the relationship between different TSH groups and the risk of adverse outcomes.

RESULTS

Among 175 112 women, a J-shaped association was revealed between TSH and large for gestational age (LGA; P < 0.001). When TSH was lower than 1.27 or 0.91 mIU/L, lower TSH was associated with higher odds ratio of low birth weight (LBW; P = 0.003) or preterm delivery (P < 0.001). There was no significant association of preconception TSH with SGA, macrosomia, fetal anomalies, stillbirth, natural or induced abortion, and cesarean delivery. The range of TSH for odds ratio lower than 1.0 was within 0.91 to 1.82 mIU/L in dose-response association. Compared with TSH 0.91 to 1.82 mIU/L, TSH low (< 0.40 mIU/L and 0.40-0.90 mIU/L) and high (1.83-2.49 mIU/L, 2.50-3.99 mIU/L, and >4.00 mIU/L) were associated with higher risk of preterm delivery and LGA. There was no significant association between TSH groups and the risk of LBW except for TSH < 0.40 mIU/L.

CONCLUSION

Preconception TSH was associated with preterm delivery, LGA, and LBW. Preconception TSH had a bidirectional effect on LGA, indicating a potential mechanism regarding influence of TSH on birth weight. TSH within 0.91 to 1.82 mIU/L was the potential safe range for preconception women.

Postnatal Serum Total Thyroxine Level Associated with Short- and Long-Term Anthropometric Outcomes in Very Preterm Infants

Thyroxine (T4) importantly regulates the growth of newborns. Compared to fetuses with equivalent gestational ages, very preterm infants (VPIs) often experience relatively low thyroxinemia, with a normal thyroid-stimulating hormone (TSH) concentration < 10 μIU/mL. However, there is continued debate regarding postnatal thyroxine supplementation for VPIs with normal TSH and transitionally low thyroxinemia. Little research has explored the role of the postnatal total T4 (TT4) serum concentration on the growth of VPIs. In this study, we aim to clarify whether the postnatal thyroxine concentration is associated with the short- and long-term growth outcomes of VPIs. A total of 334 surviving VPIs in our previously reported cohort, born in the period August 2007−July 2016, were enrolled. The exposure variable was the postnatal TT4 concentration at 1 month old. The primary outcomes were body weight increments over 28 days after the screening and anthropometric outcomes at the corrected age of 24 months old. Infants with any hormonal replacement, severe brain injury, congenital anomaly, or cerebral palsy were excluded. In total, 290 (86.8%) VPIs were included for analysis. In the 28 days after thyroid function screening, the TT4 concentration was found to have a significant association with positive increments in body weight (mean increment: 25.7 g per 1 μg/dL; p < 0.001) and a positive body weight z-score (mean increment: 0.039 per 1 μg/dL; p = 0.037), determined by generalized estimating equation analysis. At the corrected age of 24 months old, a higher postnatal TT4 concentration was associated with a lower body mass index (mean coefficient: −0.136; 95% CI: −0.231 to −0.041, p = 0.005) and lower body mass index z-score (mean coefficient: −0.097; 95% CI: −0.170 to −0.024, p = 0.009). Infants with a TT4 concentration > 6.4 ug/dL had significantly lower odds of overweight status (odds ratio: 0.365; 95% CI: 0.177 to 0.754, p = 0.006). We conclude that the postnatal TT4 concentration is associated with a positive increment in body weight in the short term. At the same time, the postnatal TT4 concentration is associated with lower odds of overweight status after long-term follow-up.

Association between maternal thyroid function and risk of gestational hypertension and pre-eclampsia: a systematic review and individual-participant data meta-analysis

BACKGROUND

Adequate maternal thyroid function is important for an uncomplicated pregnancy. Although multiple observational studies have evaluated the association between thyroid dysfunction and hypertensive disorders of pregnancy, the methods and definitions of abnormalities in thyroid function tests were heterogeneous, and the results were conflicting. We aimed to examine the association between abnormalities in thyroid function tests and risk of gestational hypertension and pre-eclampsia.

METHODS

In this systematic review and meta-analysis of individual-participant data, we searched MEDLINE (Ovid), Embase, Scopus, and the Cochrane Database of Systematic Reviews from date of inception to Dec 27, 2019, for prospective cohort studies with data on maternal concentrations of thyroid-stimulating hormone (TSH), free thyroxine (FT₄), thyroid peroxidase (TPO) antibodies, individually or in combination, as well as on gestational hypertension, pre-eclampsia, or both. We issued open invitations to study authors to participate in the Consortium on Thyroid and Pregnancy and to share the individual-participant data. We excluded participants who had pre-existing thyroid disease or multifetal pregnancy, or were taking medications that affect thyroid function. The primary outcomes were documented gestational hypertension and pre-eclampsia. Individual-participant data were analysed using logistic mixed-effects regression models adjusting for maternal age, BMI, smoking, parity, ethnicity, and gestational age at blood sampling. The study protocol was registered with PROSPERO, CRD42019128585.

FINDINGS

We identified 1539 published studies, of which 33 cohorts met the inclusion criteria and 19 cohorts were included after the authors agreed to participate. Our study population comprised 46 528 pregnant women, of whom 39 826 (85·6%) women had sufficient data (TSH and FT₄ concentrations and TPO antibody status) to be classified according to their thyroid function status. Of these women, 1275 (3·2%) had subclinical hypothyroidism, 933 (2·3%) had isolated hypothyroxinaemia, 619 (1·6%) had subclinical hyperthyroidism, and 337 (0·8%) had overt hyperthyroidism. Compared with euthyroidism, subclinical hypothyroidism was associated with a higher risk of pre-eclampsia (2·1% vs 3·6%; OR 1·53 [95% CI 1·09-2·15]). Subclinical hyperthyroidism, isolated hypothyroxinaemia, or TPO antibody positivity were not associated with gestational hypertension or pre-eclampsia. In continuous analyses, both a higher and a lower TSH concentration were associated with a higher risk of pre-eclampsia (p=0·0001). FT₄ concentrations were not associated with the outcomes measured.

INTERPRETATION

Compared with euthyroidism, subclinical hypothyroidism during pregnancy was associated with a higher risk of pre-eclampsia. There was a U-shaped association of TSH with pre-eclampsia. These results quantify the risks of gestational hypertension or pre-eclampsia in women with thyroid function test abnormalities, adding to the total body of evidence on the risk of adverse maternal and fetal outcomes of thyroid dysfunction during pregnancy. These findings have potential implications for defining the optimal treatment target in women treated with levothyroxine during pregnancy, which needs to be assessed in future interventional studies.

FUNDING

Arkansas Biosciences Institute and Netherlands Organization for Scientific Research.

Relationship Between Subclinical Hypothyroidism in Pregnancy and Hypertensive Disorder of Pregnancy: A Systematic Review and Meta-Analysis

OBJECTIVE

Studies have shown a high incidence of subclinical hypothyroidism in pregnancy, but the adverse pregnancy outcomes caused by it are not clear. Therefore, we conducted a systematic review and meta-analysis to evaluate the relationship between subclinical hypothyroidism in pregnancy and hypertensive disorders of pregnancy(HDP) to guide clinical practice.

METHOD

We searched the MEDLINE (PubMed), Cochrane Central, EMBASE, Web of Science, and SCOPUS databases and screened all studies evaluating the relationship between subclinical hypothyroidism in pregnancy and hypertensive disorders of pregnancy. Two researchers independently evaluated the quality of all eligible original studies using the Newcastle-Ottawa Scale (NOS). We also performed a meta-analysis using STATA15.1. Sensitivity analyses were also performed by examining the effects of individual studies as well as using different effect models and detecting any publication bias using the harbord test.

RESULTS

Twenty-two studies were included in the final meta-analysis. Our results indicated that pregnant women with subclinical hypothyroidism had an increased risk of HDP (OR = 1.54(95% CI: 1.21-1.96) I²=67.1%), compared with euthyroidism. Subclinical hypothyroidism in pregnancy was not associated with hypertensive disorders of pregnancy at TSH diagnostic cut-off of less than 3.0 mIU/L (P = 0.077). Curiously, the risk of HDP increases when the TSH diagnostic cut-off value is higher or lower than 4 mIU/L. Although only 9 studies were above the threshold, the risk of developing HDP was still 1.69 times, which was highest in all subgroup analyses. This is consistent with the newly recommended diagnostic cut-off value of 4 mIU/L for TSH by the ATA. Our results consider that the risk of hypertensive disorder complicating pregnancy is increased regardless of the diagnosis of subclinical hypothyroidism at any stage of pregnancy. Unfortunately, there is insufficient evidence to support that patients can benefit from treatment with levothyroxine.

CONCLUSION

The results of this meta-analysis indicate that subclinical hypothyroidism in pregnancy is associated with an increased risk of developing HDP, and this association exists regardless of the gestational period. However, the available evidence cannot support these patients receiving thyroxine intervention can benefit from it, so routine screening is only recommended for pregnant women with risk factors for hypothyroidism. Further research is needed to validate more scientific and rigorous clinical studies to clarify the relationship between subclinical hypothyroidism and HDP to improve patient prognosis.

SYSTEMATIC REVIEW REGISTRATION

https://www.crd.york.ac.uk/prospero/, PROSPERO (CRD42021286405).

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.

Controversial Screening for Thyroid Dysfunction in Preconception and Pregnancy: An Evidence-Based Review

Objective: To evaluate the recommendations on the most adequate screening method (universal or selective) for thyroid dysfunction. Although thyroid dysfunction is a common disorder in fertile women and untreated cases may have negative maternal, fetal and neonatal outcomes, its screening in preconception and early pregnancy is controversial.

Materials and methods: An evidence-based review was conducted to identify publications since 2017 of American Thyroid Association (ATA) guidelines, according to the following Population, Intervention, Comparison, Outcomes and Study (PICOS): women in preconception or pregnancy without thyroid disease who underwent universal or selective screening for thyroid dysfunction. Study selection obeyed the PRISMA criteria.

Results: We included 15 of 325 publications. The 2017 ATA guidelines recommend selective screening in both preconception and pregnancy. The only two reviews on preconception recommended universal screening. For pregnancy, nine articles suggested universal screening, while a prospective study advocated selective screening. The main benefits advocated for universal screening were easy and low-cost tests; absence of missed diagnosis; safe and inexpensive treatment and its potential in preventing negative outcomes. Iodine deficiency is a decisive indication, but it was not evaluated in all clinical studies. Screening harms and knowledge gaps were the main arguments against universal screening. There are very few cost-effectiveness studies.

Conclusion: We recommend universal screening for thyroid dysfunction in early pregnancy, which is a distinct point of view from 2017 ATA guidelines (weak recommendation, low-quality evidence). It is not possible to make a formal recommendation for preconception (insufficient evidence). We strongly suggest an individualized analysis by each country.

Relationship between anti-thyroid peroxidase antibody positivity and pregnancy-related and fetal outcomes in Euthyroid women: a single-center cohort study

BACKGROUND

Thyroid autoimmunity (TAI) and subclinical hypothyroidism (SCH) have been associated with poor pregnancy and fetal outcomes. However, whether euthyroid women with anti-thyroid peroxidase antibody (TPOAb) positivity have a higher risk of poor pregnancy and fetal outcomes is debatable. Therefore, this study aimed to investigate the association between TPOAb positivity and pregnancy-related and fetal outcomes in euthyroid women.

METHODS

In total, 938 pregnant women participated in this prospective cohort study. The euthyroid group included 837 pregnant women and the TPOAb-positive group included 101 euthyroid pregnant women. Serum TPOAb, thyroglobulin antibody (TGAb), thyroid-stimulating hormone (TSH), and free thyroxine (FT4) levels were assessed. Pregnancy and fetal outcomes included gestational diabetes mellitus, spontaneous abortion, premature rupture of membranes, hypertensive disorders of pregnancy, preterm birth, fetal distress, low birth weight, fetal macrosomia, and small for gestational age infant.

RESULTS

Logistic regression analysis showed TPOAb positivity was not associated with an increased risk of poor pregnancy or fetal outcomes in euthyroid women. However, TPOAb-positive euthyroid women pregnant with a female fetus were independently associated with preterm births (OR: 4.511, 95% CI: 1.075-18.926) after adjustment for potential confounding factors.

CONCLUSIONS

TPOAb positivity was not found to be associated with poor pregnancy-related or fetal outcomes in euthyroid women. However, in euthyroid women with a female fetus, TPOAb positivity was strongly associated with preterm births. The risk of preterm birth in the euthyroid women with TPOAb positivity should be emphasized in clinical practice.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT02966405 . Registered on October 24th 2016 - Retrospectively registered.

Does Maternal Normal Range Thyroid Function Play a Role in Offspring Birth Weight? Evidence From a Mendelian Randomization Analysis

BACKGROUND

The association between normal range thyroid function and offspring birth weight has been postulated, but evidence from observational studies is prone to be confounded. We conducted a two-sample Mendelian randomization (MR) study to explore the causal effects of maternal thyroid stimulating hormone (TSH) and free thyroxine (FT4) on birth weight.

METHODS

We utilized public shared summary-level statistics from European-ancestry genome wide association studies. We obtained 40 and 21 single nucleotide polymorphisms as instrumental variables, which were associated with TSH and FT4 levels at genome-wide significance (P < 5 × 10^-8). Partitioned maternal effects on birth weight were retrieved from datasets contributed by the Early Growth Genetics Consortium. Inverse-variance weighted method was employed in the primary MR analysis and multiple sensitivity analyses were implemented.

RESULTS

Genetically determined normal range thyroid function was not causally associated with offspring birth weight. Each one standard deviation (SD) increase in maternal TSH was associated with 0.002 SD higher of birth weight (95% confidence interval [CI], -0.021 to 0.025; P = 0.87). Similarly, change in birth weight was -0.001 SD (95% CI, -0.031 to 0.029; P = 0.94) per one SD higher in maternal FT4. Consistent results were yielded via additional MR methods. Sensitivity analyses demonstrated no presence of horizontal pleiotropy or heterogeneity.

CONCLUSION

This MR study did not identify a causality between normal range thyroid function and offspring birth weight in the Europeans.