Maternal early-pregnancy thyroid function is associated with subsequent hypertensive disorders of pregnancy: the generation R study

Emerging research themes in maternal hypothyroidism: a bibliometric exploration

Background

Hypothyroidism, a prevalent endocrine disorder, carries significant implications for maternal and infant health, especially in the context of maternal hypothyroidism. Despite a gradual surge in recent research, achieving a comprehensive understanding of the current state, focal points, and developmental trends in this field remains challenging. Clarifying these aspects and advancing research could notably enhance maternal-infant health outcomes. Therefore, this study employs bibliometric methods to systematically scrutinize maternal hypothyroidism research, serving as a reference for further investigations.

Objective

Through bibliometric analysis, this study seeks to unveil key research focus areas, developmental trends, and primary contributors in Maternal Hypothyroidism. The findings offer insights and recommendations to inform future research endeavors in this domain.

Methods

Literature metrics analysis was performed on data retrieved and extracted from the Web of Science Core Collection database. The analysis examined the evolution and thematic trends of literature related to Maternal Hypothyroidism. Data were collected on October 28, 2023, and bibliometric analysis was performed using VOSviewer, CiteSpace, and the Bibliometrix software package, considering specific characteristics such as publication year, country/region, institution, authorship, journals, references, and keywords.

Results

Retrieved from 1,078 journals, 4,184 articles were authored by 18,037 contributors in 4,580 institutions across 113 countries/regions on six continents. Maternal Hypothyroidism research publications surged from 44 to 310 annually, a 604.54% growth from 1991 to 2022. The USA (940 articles, 45,233 citations), China Medical University (82 articles, 2,176 citations), and Teng, Weiping (52 articles, 1,347 citations) emerged as the most productive country, institution, and author, respectively. "Thyroid" topped with 233 publications, followed by "Journal of Clinical Endocrinology & Metabolism" (202) with the most citations (18,513). "Pregnancy" was the most cited keyword, with recent high-frequency keywords such as "outcome," "gestational diabetes," "iodine intake," "preterm birth," "guideline," and "diagnosis" signaling emerging themes in Maternal Hypothyroidism.

Conclusions

This study unveils developmental trends, global collaboration patterns, foundational knowledge, and emerging frontiers in Maternal Hypothyroidism. Over 30 years, research has predominantly focused on aspects like diagnosis, treatment guidelines, thyroid function during pregnancy, and postpartum outcomes, with a central emphasis on the correlation between maternal and fetal health.

Management of Hyperthyroidism during Pregnancy: A Systematic Literature Review

In pregnancy, several physiological changes affect maternal circulating thyroid hormone levels. The most common causes of hyperthyroidism in pregnancy are Graves' disease and hCG-mediated hyperthyroidism. Therefore, evaluating and managing thyroid dysfunction in women during pregnancy should ensure favorable maternal and fetal outcomes. Currently, there is no consensus regarding an optimal method to treat hyperthyroidism in pregnancy. The term "hyperthyroidism in pregnancy" was searched in the PubMed and Google Scholar databases to identify relevant articles published between 1 January 2010 and 31 December 2021. All of the resulting abstracts that met the inclusion period were evaluated. Antithyroid drugs are the main therapeutic form administered in pregnant women. Treatment initiation aims to achieve a subclinical hyperthyroidism state, and a multidisciplinary approach can facilitate this process. Other treatment options, such as radioactive iodine therapy, are contraindicated during pregnancy, and thyroidectomy should be limited to severe non-responsive thyroid dysfunction pregnant patients. In light of this events, even in the absence of guidelines certifying screening, it is recommended that all pregnant and childbearing women should be screened for thyroid conditions.

Thyroid autoimmunity and adverse pregnancy outcomes: A multiple center retrospective study

BACKGROUND

The relationship between thyroid autoimmunity (TAI) and adverse pregnancy outcomes is disputable, and their dose-dependent association have not been fully clarified.

OBJECTIVE

To investigate the association and dose-dependent effect of TAI with multiple maternal and fetal-neonatal complications.

METHODS

This study is a multi-center retrospective cohort study based on singleton pregnancies of three medical college hospitals from July 2013 to October 2021. The evolution of thyroid function parameters in TAI and not TAI women were described, throughout pregnancy. The prevalences of maternal and fetal-neonatal complications were compared between the TAI and control group. Logistic regression was performed to study the risk effects and dose-dependent effects of thyroid autoantibodies on pregnancy complications, with adjustment of maternal age, BMI, gravidity, TSH concentrations, FT4 concentrations and history of infertility.

RESULTS

A total of 27408 participants were included in final analysis, with 5342 (19.49%) in the TAI group and 22066 (80.51%) in control group. TSH concentrations was higher in TAI women in baseline and remain higher before the third trimester. Positive thyroid autoantibodies were independently associated with higher risk of pregnancy-induced hypertension (OR: 1.215, 95%CI: 1.026-1.439), gestational diabetes mellitus (OR: 1.088, 95%CI: 1.001-1.183), and neonatal admission to NICU (OR: 1.084, 95%CI: 1.004-1.171). Quantitative analysis showed that increasing TPOAb concentration was correlated with higher probability of pregnancy-induced hypertension, and increasing TGAb concentration was positively correlated with pregnancy-induced hypertension, small for gestational age and NICU admission. Both TPOAb and TGAb concentration were negatively associated with neonatal birthweight.

CONCLUSION

Thyroid autoimmunity is independently associated with pregnancy-induced hypertension, gestational diabetes mellitus, neonatal lower birthweight and admission to NICU. Dose-dependent association were found between TPOAb and pregnancy-induced hypertension, and between TGAb and pregnancy-induced hypertension, small for gestational age and NICU admission.

A Prospective Study to Determine the Predictive Ability of HDP-Gestosis Score for the Development of Pre-eclampsia

Background

HDP-gestosis score is a risk scoring system (score 1-3) for the development of pre-eclampsia. When a pregnant woman's total score is equal to or greater than 3, she is labelled as "at risk for pre-eclampsia" and is managed accordingly.

Objectives

To determine the sensitivity, specificity, Positive predictive value (PPV), negative predictive value (NPV) and diagnostic accuracy of HDP-gestosis score for predicting pre-eclampsia.

Methods

This prospective study included 473 pregnant women who presented at the department of Obstetrics and Gynaecology, from June 2020 to December 2021. After 20 weeks of pregnancy, the patients were assessed for the development of pre-eclampsia. Details of age, gravida, obstetric history, menstrual cycle regularity, polycystic ovarian disease history, duration of marriage, parity, past medical and surgical intervention, previous/present medication, and family history were taken. Gestosis score was calculated and classified into mild (score of 1), moderate (score of 2) and high risk (score of ≥ 3) for the development of Pre-eclampsia (PE). Sensitivity, Specificity, PPV, NPV and diagnostic accuracy of HDP-gestosis score for predicting the development of PE were determined.

Results

The mean age, gestational age, and BMI of the women were 28.4 ± 6.8 years, 11.5 ± 2.04 weeks, and 24.5 ± 3.7 kg/m^2, respectively. The gestosis score was 2 in 43.13% of the participants, 1 in 42.28%, and ≥ 3 in 14.59% of the women. PE developed in 15.01% (n = 71) participants. The Sensitivity, Specificity, PPV, NPV, and Diagnostic accuracy of HDP-gestosis score for predicting PE were 83.1%, 97.51%, 85.51%, 97.03% and 95.35%, respectively.

Conclusion

Gestosis score is a novel early marker for prediction of the development of PE allowing for a prompt management for the patients, thereby curbing the adverse consequences.

Obstetric and offspring outcomes in isolated maternal hypothyroxinaemia: a systematic review and meta-analysis

OBJECTIVE

To examine the association between isolated maternal hypothyroxinaemia (IMH) and adverse obstetric outcomes and offspring outcomes and also investigate the effects of levothyroxine therapy on IMH for the above outcomes.

METHODS

We systematically searched PubMed, EMBASE, and Cochrane Library, and the reference lists of key reviews were hand searched on June 9, 2021. Two authors independently screened titles/abstracts. Full articles were further assessed if the information suggested that the study met the inclusion/exclusion criteria, and two researchers performed data extraction and risk-of-bias assessment using standardized tables. Summary relative risks or the mean difference between maternal effects and offspring outcomes were calculated by a random-effects model.

RESULTS

We identified 38 eligible articles (35 cohort studies and two randomized controlled trials [RCT]). Meta-analysis showed that maternal IMH was associated with increased gestational diabetes mellitus, preterm premature rupture of membranes, preterm birth, fetal distress, and macrosomia outcomes in IMH compared to euthyroid women, and the relative risks were 1.42 (1.03-1.96), 1.50 (1.05-2.14), 1.33 (1.15-1.55), 1.75 (1.16-2.65) and 1.62 (1.35-1.94), respectively. IMH was not associated with placenta previa, gestational hypertension, pre-eclampsia, intrauterine growth restriction, and offspring outcomes like birth weight, low birth weight infants, fetal macrosomia, neonatal intensive care, neonatal death, or fetal head circumference. In addition, we did not find an association between IMH and adverse offspring cognitive defects. Due to insufficient data for meta-analysis, it failed to pool the evidence of levothyroxine's therapeutic effect on IMH and their offspring.

CONCLUSIONS AND RELEVANCE

IMH in pregnancy may relate to a few maternal and offspring outcomes. Moreover, there is currently no sufficient evidence that levothyroxine treatment during pregnancy reduces adverse maternal outcomes and disability in offspring. Further investigation to explore the beneficial effects of levothyroxine therapy is warranted.

Evaluating thyroid function in pregnant women

Thyroid hormones are primarily responsible for regulating the basal metabolic rate but also make important contributions to reproductive function and fetal development. Both hyper- and hypothyroidism in pregnancy have been associated with increased risks of complications that include preeclampsia and low birth weight, among others. Furthermore, thyroid hormone deficiency in the developing fetus results in neurodevelopmental delay. As the fetus is exclusively reliant on maternal thyroid hormone for most of the first trimester and requires continued maternal supply until birth, identifying maternal thyroid dysfunction is critically important. However, evaluating thyroid function in pregnancy is challenging because of the many physiological changes that affect concentrations of thyroid-related analytes. Increasing plasma human chorionic gonadotropin (hCG) concentrations in the second half of the first trimester elicit a corresponding transient decrease in thyroid-stimulating hormone (TSH), and continually increasing estradiol concentrations throughout pregnancy cause substantial increases in thyroxine-binding globulin (TBG) and total thyroxine (T4) relative to the nonpregnant state. Lastly, free T4 concentrations gradually decrease with increasing gestational age. For these reasons, it is essential to interpret thyroid function test results in the context of trimester-specific reference intervals to avoid misclassification of thyroid status. This review summarizes the effects of thyroid dysfunction prior to conception and during pregnancy and describes considerations for the laboratory assessment of thyroid function in pregnant women.

Diagnostic and Treatment Considerations for Thyroid Cancer in Women of Reproductive Age and the Perinatal Period

Thyroid cancer is one of the most common cancers diagnosed in women of reproductive age and during pregnancy. This leads to important questions about thyroid cancer prognosis and treatment, but also fertility and risk for adverse obstetric and/or fetal and neonatal outcomes. The benefits of thyroid cancer treatment should be weighed against its harms, as various options may adversely impact maternal and fetal health. In the current review, the authors focus on perinatal-specific clinical considerations related to the care of patients with thyroid cancer.

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.

Role of Salivary Uric Acid Versus Serum Uric Acid in Predicting Maternal Complications of Pre-Eclampsia in a Rural Hospital in Central India: A Two-Year, Cross-Sectional Study

Background

Hypertensive disorders during pregnancy are an important topic of concern, specifically in rural and remote areas of India where there is a lack of awareness and it is difficult to maintain proper follow-up of pregnant females to screen them for complications developed during pregnancy. Gestational hypertension and pre-eclampsia result in the abruption of the placenta, hemolysis, elevated liver enzymes, low platelet count syndrome, eclampsia, and disseminated intravascular coagulation, which can be a serious threat to the health of the mother and the fetus. Therefore, it is important to identify biomarkers for diagnosing and predicting the complications of pre-eclampsia that may aid the obstetric high-dependency units based in rural areas to tackle this important health hazard during pregnancy.

Methodology

A total of 180 singleton pregnant women of more than 34 weeks of gestational age were enrolled in this study. All women were divided into three groups (control group, severe pre-eclampsia, and non-severe pre-eclampsia) based on the severity of blood pressure and the presence of proteinuria (≥+1 by the dipstick method). Salivary and serum uric acid levels were measured through morning samples, and all patients were monitored for the development of complications and outcomes. Salivary uric acid and serum uric acid levels were correlated with each other and with maternal complications of pre-eclampsia.

Results

Mean salivary uric acid (mg/dL) in severe pre-eclampsia was (6.72 ± 0.49) significantly higher compared to non-severe pre-eclampsia (4.75 ± 0.94) and control (3.13 ± 0.43). Mean serum uric acid (mg/dL) in severe pre-eclampsia was (8.13 ± 0.87) significantly higher compared to non-severe pre-eclampsia (6.23 ± 0.76) and control (3.85 ± 0.46).The lowest best cut-off value of maternal salivary uric acid was 5.06 mg/dL, above which one can predict maternal complications with a diagnostic accuracy of 78.33%.

Conclusions

Salivary uric acid and serum uric acid levels are significantly raised in cases of pre-eclampsia in comparison to normal pregnancy. Salivary uric acid and serum uric acid are correlated significantly indicating that salivary uric acid can function as a cost-effective, novel marker to provide an idea about serum uric acid levels. The prognostic accuracy of salivary uric acid was good in predicting maternal complications among cases of pre-eclampsia (severe and non-servere) and early-onset maternal complications. Therefore, it may be utilized as a helpful marker to identify high-risk patients.

Effect of Hyperthyroidism Control During Pregnancy on Maternal and Fetal Outcome: A Systematic Review and Meta-Analysis

CONTEXT

Although the overt hyperthyroidism treatment during pregnancy is mandatory, unfortunately, few studies have evaluated the impact of treatment on reducing maternal and fetal outcomes.

OBJECTIVE

This study aimed to demonstrate whether treatment to control hyperthyroidism manifested during pregnancy can potentially reduce maternal-fetal effects compared with euthyroid pregnancies through a systematic review with meta-analysis.

DATA SOURCE

MEDLINE (PubMed), Embase, Cochrane Library Central, LILACS/BIREME until May 2021.

STUDY SELECTION

Studies that compared, during the gestational period, treated women with hyperthyroidism versus euthyroid women. The following outcomes of this comparison were: pre-eclampsia, abruptio placentae, fetal growth retardation, gestational diabetes, postpartum hemorrhage, low birth weight, stillbirth, spontaneous abortions, premature birth.

DATA EXTRACTION

Two independent reviewers extracted data and performed quality assessments. Dichotomous data were analyzed by calculating risk differences (DR) with fixed and random effect models according to the level of heterogeneity.

DATA SYNTHESIS

Seven cohort studies were included. The results of the meta-analysis indicated that there was a lower incidence of preeclampsia (p=0.01), low birth weight (p=0.03), spontaneous abortion (p<0.00001) and preterm birth (p=0.001) favouring the euthyroid pregnant group when compared to those who treated hyperthyroidism during pregnancy. However, no statistically significant differences were observed in the outcomes: abruptio placentae, fetal growth retardation, gestational diabetes mellitus, postpartum hemorrhage, and stillbirth.

CONCLUSIONS

Our findings demonstrated that treating overt hyperthyroidism in pregnancy is mandatory and appears to reduce some potential maternal-fetal complications, despite there still being a residual risk of negative outcomes.

The application of new concepts of the assessment of the thyroid state to pregnant women

Recently proposed concepts regarding the nature and assessment of the thyroid state have provided a model more consistent with empiric evidence. It now appears likely that there are no such entities as thyroid set points and individual euthyroidism. Rather than there being discrete thyroid states, peripheral organ parameters are associated with thyroid function in a continuous manner. Thyroid hormone levels and, in particular, levels of free thyroxine now appear to be superior to thyrotropin levels as indicators of the thyroid state. Complicating the assessment of the correlations of the thyroid state with pregnancy outcomes are the contribution of the placenta to maternal thyroid function, fetal thyroid development, the multiple potential pathways to any particular outcome, the likely presence of small critical periods of time, the differing genetics of fetal and maternal tissues, and the unreliability of thyroid hormone assays. Nevertheless, there is no apparent reason for there to be a change in pregnancy to the basic principles of thyroid hormone action. The relationships between mild abnormalities of the thyroid state and pregnancy outcomes and the value of treating such mild abnormalities remain uncertain and controversial. The evidence suggests that further investigation of these clinical questions might better be based on thyroid hormone, particularly free thyroxine, levels. In the investigation of borderline low thyroid states, the categories of subclinical hypothyroidism and isolated hypothyroxinemia might both be abandoned with attention being directed to low free thyroxine levels regardless of the thyroid-stimulating hormone (TSH) levels. For these changes to occur, there would ideally be improvements in the assays for free thyroxine in pregnancy. The evidence suggests that, just as in the non-pregnant situation, pregnancy guidelines based on thyrotropin levels may need revision.

Pregnancy Outcomes in Thyroid Cancer Survivors: A Propensity Score-Matched Cohort Study

BACKGROUND

Some female thyroid cancer survivors wish to become pregnant following their cancer treatment. Current studies have shown inconsistent results on pregnancy outcomes in these survivors; however, detailed information on the pathological type, treatment, and gestational thyroid function of these patients are not yet well documented, making the refined assessment of the influence of a history of thyroid cancer and related treatments on pregnancy outcomes challenging.

OBJECTIVE

To investigate the risk of adverse pregnancy outcomes in thyroid cancer survivors.

METHODS

This was a retrospective cohort study. We included all women aged between 19 and 45 years old who delivered between January 2019 and June 2020 in West China Second University Hospital of Sichuan University. Women with tumors other than thyroid cancer or other thyroid diseases were excluded. The included women were divided into survivors of thyroid cancer (survivors) and women without any history of thyroid disease (controls). Propensity score matching and logistic regression were used to control confounding variables.

RESULTS

All 18,332 women who met the inclusion criteria were included in the study (96 survivors of papillary thyroid cancer and 18,236 controls). After propensity score matching, 96 survivors and 192 controls were included. The survivors had higher levels of free thyroxine (15.47 [13.61-17.67] vs. 14.38 [13.20-15.81] pmol/mL; P<0.001) and higher levels of thyroid peroxidase antibodies (TPOAb) (43.55 [31.43-71.43] vs. 35.95 [28.00-48.03] U/mL; P=0.008) but similar levels of thyroid stimulating hormone (1.46 [0.56-3.15] vs. 1.36 [0.81-1.92] mIU/mL; P=0.142) than the controls. There were no significant differences in adverse pregnancy outcomes between survivors and controls. Fetal macrosomia was lower among survivors (OR: 0.077, 95% CI: 0.009-0.668. P=0.020) than controls. Additionally, survivors had reduced weight gain during pregnancy (13.0 [10.0-15.0] vs. 14.00 [11.00-16.00] kg, P=0.005) and reduced placental weight (563.0 [514.5-620.0] vs. 572.0 [520.0-650.0] g, P=0.019), albeit with small absolute differences. Thyroidectomy or radioiodine therapy did not adversely affect pregnancy outcomes.

CONCLUSION

A history of treated papillary thyroid cancer was not associated with adverse pregnancy outcomes.

Identifying Non-Linear Association Between Maternal Free Thyroxine and Risk of Preterm Delivery by a Machine Learning Model

OBJECTIVE

Preterm delivery (PTD) is the primary cause of mortality in infants. Mounting evidence indicates that thyroid dysfunction might be associated with an increased risk of PTD, but the dose-dependent association between the continuous spectrum maternal free thyroxine (FT4) and PTD is still not well-defined. This study aimed to further investigate this relationship using a machine learning-based model.

METHODS

A hospital-based cohort study was conducted from January 2014 to December 2018 in Shanghai, China. Pregnant women who delivered singleton live births and had first-trimester thyroid function data available were included. The generalized additive models with penalized cubic regression spline were applied to explore the non-linear association between maternal FT4 and risk of PTD and also subtypes of PTD. The time-to-event method and multivariable Cox proportional hazard model were further applied to analyze the association of abnormally high and low maternal FT4 concentrations with the timing of PTD.

RESULTS

A total of 65,565 singleton pregnancies with completed medical records and no known thyroid disease before pregnancy were included for final analyses. There was a U-shaped dose-dependent relationship between maternal FT4 in the first trimester and PTD (p <0.001). Compared with the normal range of maternal FT4, increased risk of PTD was identified in both low maternal FT4 (<11.7 pmol/L; adjusted hazard ratio [HR] 1.34, 95% CI [1.13-1.59]) and high maternal FT4 (>19.7 pmol/L; HR 1.41, 95% CI [1.13-1.76]). The association between isolated hypothyroxinemia and PTD was mainly associated with spontaneous PTD (HR 1.33, 95% CI [1.11-1.59]) while overt hyperthyroidism may be attributable to iatrogenic PTD (HR 1.51, 95% CI [1.18-1.92]) when compared with euthyroid women. Additionally, mediation analysis identified that an estimated 11.80% of the association between overt hyperthyroidism and iatrogenic PTD risk was mediated via the occurrence of hypertensive disorders in pregnancy (p <0.001).

CONCLUSIONS

We revealed a U-shaped association between maternal FT4 and PTD for the first time, exceeding the clinical definition of maternal thyroid function test abnormalities. Our findings provide insights towards the need to establish optimal range of maternal FT4 concentrations for preventing adverse outcomes in pregnancy.

Urinary iodine as an important indicator for preeclampsia: a Polish perspective

Preeclampsia (PE) is one of the leading causes of perinatal and maternal morbidity. Although subclinical hypothyroidism in pregnancy is one of the established risk factors for PE, the link between iodine deficiency and PE is not fully understood. The aim of our study was to assess urinary iodine concentration (UIC), serum thyroid-stimulating hormone (TSH), free triiodothyronine (fT3), and free thyroxine (fT4) levels in Polish women with PE (PE group, n=78) compared with healthy non-pregnant women (CNP group, n=30), and healthy pregnant women (CP group, n=46). The UIC was determined by inductively coupled plasma mass spectrometry (ICP-MS). Both the mean UIC of 144.6±36.4 μg/L in the CP group and the mean of 125.8±33.6 μg/L in the PE group, respectively, were lower compared to non-pregnant women (149.8±28.8 μg/L), and the difference between the PE and CNP groups was statistically significant. TSH values were the highest in the PE group, while the lowest average level was for the CNP group. The fT3 and fT4 values in the PE group were significantly lower compared to the CNP and CP groups. Despite iodine supplementation during pregnancy, the UIC was lower compared to non-pregnant women, while in women with PE it was at a significantly lower level. To reduce the incidence of possible health complications, proper iodine supplementation and monitoring of the UIC is recommended for pregnant women suffering from PE or at risk of developing PE.

The association between COVID-19 pandemic and maternal isolated hypothyroxinemia in first and second trimesters

BACKGROUND

The outbreak of COVID-19 epidemic has induced entire cities in China placed under 'mass quarantine'. The majority of pregnant women have to be confined at home may be more vulnerable to stressors. In our study, we aimed to explore the effects of the epidemic on maternal thyroid function, so as to provide evidence for prevention and intervention of sustained maternal and offspring's health impairment produced by thyroid dysfunction.

METHODS

The subjects were selected from an ongoing prospective cohort study. we included the pregnant women who receive a thyroid function test during the COVID-19 epidemic and those receiving the test during the corresponding lunar period of 2019. A total of 7148 pregnant women with complete information were included in the final analysis. Multivariate linear and logistic regression models were used for analyzing the association of COVID-19 pandemic with FT4 levels and isolated hypothyroxinemia.

RESULTS

We found a decreased maternal FT4 level during the period of the COVID-19 pandemic in first and second trimesters (β = -0. 131, 95%CI = -0.257,-0.006，p = 0.040) and in first trimester (β = -0. 0.176, 95%CI = -0.326,-0.026，p = 0.022) when adjusting for 25 (OH) vitamin D, vitamin B12, folate and ferritin and gestational days, maternal socio-demographic characteristics and health conditions. The status of pandemic increased the risks of isolated hypothyroxinemia in first and second trimesters (OR = 1.547, 95%CI = 1.251,1.913, p < 0.001) and first trimester (OR = 1.651, 95%CI = 1.289,2.114, p < 0.001) when adjusting for the covariates. However, these associations disappeared in the women with positive TPOAb (p > 0.05). Additionally, we found associations between daily reported new case of COVID-19 and maternal FT4 for single-day lag1, lag3 and multi-day lag01 and lag04 when adjusting for the covariates (each p < 0.05).

CONCLUSIONS

Mass confinement as a primary community control strategy may have a significant cost to public health resources. Access to health service systems and adequate medical resources should be improved for pregnant women during the COVID-19 pandemic.

Thyroid function modifications in women undergoing controlled ovarian hyperstimulation for in vitro fertilization: a systematic review and meta-analysis

OBJECTIVE

To investigate the impact of controlled ovarian hyperstimulation (COH) for in vitro fertilization (IVF) on thyroid function.

DESIGN

Systematic review and meta-analysis.

SETTING

Not applicable.

PATIENT(S)

Infertile women undergoing conventional IVF or intracytoplasmic sperm injection.

INTERVENTION(S)

Systematic search of PubMed, MEDLINE, Embase, Scopus, and Web of Science from inception until November 2020. Studies could be included only if they met the following criteria: subjects were classified as euthyroid or hypothyroid; serum thyroid-stimulating hormone (TSH) and/or free thyroxine (FT4) levels were evaluated before COH; and the same thyroid function test was reassessed after COH (i.e., at the time of trigger for final follicle maturation and/or at pregnancy test).

MAIN OUTCOME MEASURE(S)

Mean difference (MD) between the serum TSH or FT4 levels assessed after COH and before COH.

RESULT(S)

In euthyroid women, the serum TSH levels assessed at the time of trigger and at the time of pregnancy test were significantly higher than those at baseline (MD: 0.69 mIU/L, 95% confidence interval [CI]: 0.30-1.08, I² = 93% and MD: 0.67, 95% CI: 0.49-0.85, I² = 72%, respectively). The serum FT4 levels did not undergo significant changes. Subanalysis confirmed an increase in the TSH level after restricting the analysis to women treated with gonadotropin-releasing hormone agonist protocols and to those who achieved pregnancy. A pronounced increase in the TSH level was observed in women treated for hypothyroidism (MD: 1.50 mIU/L, 95% CI: 1.10-1.89, I² = 0%).

CONCLUSION(S)

Pooling of the results showed a significant increase in serum TSH level in women undergoing COH for IVF. This change was particularly pronounced in women treated for hypothyroidism. New thyroid function screening strategies for women undergoing COH are warranted.

Thyroid Function Test Abnormalities in Twin Pregnancies

Background: Compared with singletons, a twin pregnancy is associated with a larger thyroid hormone demand and an increased stimulation of gestational thyroid function due to higher concentrations of human chorionic gonadotropin. However, such effects have been sparsely quantified. The aim of this study was to evaluate thyroid function and thyroid function test abnormalities in twin pregnancies during early and late pregnancy compared with singletons. Methods: We included 1208 twin pregnancies and 46,834 singleton pregnancies with thyroid function tests available. Thyroid function test abnormalities were defined using population-based reference ranges. The analyses were adjusted for potential confounders including maternal age and body mass index. Results: Compared with singletons, a twin pregnancy was associated with a lower thyrotropin (TSH) (β = -0.46 [95% confidence interval, CI -0.49 to -0.44], p < 0.001) and a higher free thyroxine (fT4) (β = 0.91 [CI 0.69-1.16], p < 0.001) during early pregnancy. During late pregnancy, a twin pregnancy was associated with a higher TSH (β = 0.35 [CI 0.29-0.42], p < 0.001) while fT4 did not differ (β = -0.11 [CI -0.22 to 0.01], p = 0.065). During early pregnancy, a twin pregnancy was associated with a higher risk of overt hyperthyroidism (odds ratio, OR = 7.49 [CI 6.02-9.33], p < 0.001), subclinical hyperthyroidism (OR = 5.26 [CI 4.17-6.64], p < 0.001), and isolated hypothyroxinemia (OR = 1.89 [CI 1.43-2.49], p < 0.001), but with a lower risk of subclinical hypothyroidism (OR = 0.27 [CI 0.13-0.54], p < 0.001). In late pregnancy, a twin pregnancy was associated with a higher risk of subclinical hypothyroidism (OR = 4.05 [CI 3.21-5.11], p < 0.001), isolated hypothyroxinemia (OR = 1.48 [CI 1.04-2.10], p = 0.028), and subclinical hyperthyroidism (OR = 1.76 [CI 1.27-2.43], p < 0.001). Conclusions: During early pregnancy, a twin pregnancy was associated with a higher thyroid function and a higher risk of (subclinical) hyperthyroidism, as well as a higher risk of isolated hypothyroxinemia. During late pregnancy, a twin pregnancy was associated with a higher TSH concentration and a higher risk of subclinical hypothyroidism, as well as a persistently higher risk of isolated hypothyroxinemia and subclinical hyperthyroidism. The study was approved by Chinese Clinical Trial Registry (registration no. ChiCTR1800014394).

The role of thyroid-stimulating hormone and thyroglobulin antibody in abnormally invasive placenta

PURPOSE

Thyroid hormones and antibodies are known to participate in angiogenesis and invasion and also thyroid hormone receptors are expressed in the placenta. We aimed to evaluate the relationship of serum levels of thyroid-stimulating hormone (TSH), thyroid hormones (TH), and anti-thyroid antibodies with abnormally invasive placenta (AIP). We also aimed to investigate whether they are related with cesarean hysterectomy and massive blood transfusion need in AIP cases.

METHODS

A total of 88 pregnant patients were enrolled in this prospective case-control study (30 with AIP, 28 with non-adherent placenta previa totalis (PPT) and 30 controls). Serum TSH, thyroid hormone [T3 (triiodothyronine) and T4 (thyroxine)] and thyroid antibodies against thyroglobulin (TgAb) and thyroid peroxidase (TPOAb) levels were studied in maternal serum at initial admission to our Perinatology Unit (at early third trimester). The factors associated with increased risk of AIP, cesarean hysterectomy, massive blood transfusion, and adverse perinatal outcomes were evaluated with multiple logistic regression analysis. Adjusted odds ratios and 95% confidence intervals were also calculated.

RESULTS

Serum TSH and TgAb levels were significantly lower in the AIP group than both PPT and control groups (p = .01, p < .001 and p < .001, p < .001 respectively). Decreased serum levels of TSH (<2.16 mIU/L) and TgAb (<2.70 mIU/L) levels and high previous cesarean section rates were found to be independently associated with AIP in pregnant women with PPT (OR: 0.4, 95% CI: 0.1-0.9; p = .04, OR: 0.7, 95%CI: 0.4-1.3, p = .02 and OR: 0.1, 95% CI: 0.1-0.5, p = .01). Decreased serum TSH and TgAb levels were found to be independently associated with an increased rate of cesarean hysterectomy and massive blood transfusion in AIP cases (OR: 3.7, 95% CI: 1.4-9.8; p = .01, OR: 1.8, 95% CI: 1.1-3.1; p = .03 and OR: 2.6, 95% CI: 1.0-6.5; p = .05, OR: 2.2, 95% CI: 1.1-4.1 p = .02). Decreased TSH and TgAb serum levels were also found to be independently associated with adverse perinatal outcomes in AIP cases (OR: 3.4, 95% CI: 1.3-11.0; p = .01 and OR: 1.978, 95% CI: 2-3.6; p = .03).

CONCLUSION

Decreased serum TSH and TgAb levels, and previous history of cesarean section were all found to be significantly associated with AIP in cases with PPT. We suggest that maternal serum TSH and TgAb levels can provide additional contribution to obstetric Doppler ultrasound in the diagnosis of AIP and thus can reduce the risks of unplanned cesarean hysterectomy in cases with PPT.

Isolated maternal hypothyroxinemia and adverse pregnancy outcomes: A systematic review

Maternal thyroid hormones are vital for a normal pregnancy and the development of fetus and childhood; inadequate availability of thyroid hormones during pregnancy is associated with adverse pregnancy outcomes. Isolated maternal hypothyroxinemia (IMH) is defined as a low maternal T4 in the absence of TSH elevation. This systematic review aimed to investigate the association between IMH and adverse pregnancy outcomes. PubMed, Scopus and Web of science were searched for retrieving observational studies published up to September 2020, investigating the association of IMH with adverse pregnancy outcomes. From a total of 308 articles, 17 met our eligibility criteria and were used for the purpose of the present study. Definition of IMH varied in different studies. While some studies reported no adverse pregnancy outcomes for IMH, other studies found a positive association between first trimester IMH and feto-maternal outcomes including gestational hypertension, gestational diabetes, preterm delivery, fetal distress, small for gestational age, musculoskeletal malformations, spontaneous abortion, placental abruption and macrosomia. IMH, identified in the second trimester was associated with an increase in the risk of gestational diabetes, and hypertensive disorders of pregnancy in one study. There is no consensus on the adverse effects of IMH on pregnancy outcomes. Further comprehensive cohort studies using one standard definition for IMH, with large sample size and control of important confounders such as iodine status and maternal Thyroid peroxidase antibody (TPOAb) are needed for precise assessment of this association.

Understanding the Pathogenesis of Gestational Hypothyroidism

Pregnancy is a complex state with many endocrinological challenges to a woman's physiology. Gestational Hypothyroidism (GHT) is an emerging condition where insufficiency of the thyroid gland has developed during pregnancy in a previously euthyroid woman. It is different to overt hypothyroidism, where marked elevation of thyroid-stimulating hormone with corresponding reduction in free thyroxine levels, is well known to cause detrimental effects to both the mother and the baby. During the past couple of decades, it has been shown that GHT is associated with multiple adverse maternal and fetal outcomes such as miscarriage, pre-eclampsia, placental abruption, fetal loss, premature delivery, neurocognitive and neurobehavioral development. However, three randomized controlled trials and a prospective cohort study performed within the last decade, show that there is no neurodevelopmental improvement in the offspring of mothers who received levothyroxine treatment for GHT. Thus, the benefit of initiating treatment for GHT is highly debated within the clinical community as there may also be risks associated with over-treatment. In addition, regulatory mechanisms that could possibly lead to GHT during pregnancy are not well elucidated. This review aims to unravel pregnancy induced physiological challenges that could provide basis for the development of GHT. During pregnancy, there is increased renal clearance of iodine leading to low iodine state. Also, an elevated estrogen level leading to an increase in circulating thyroglobulin level and a decrease in free thyroxine level. Moreover, placenta secretes compounds such as human chorionic gonadotropin (hCG), placental growth factor (PIGF) and soluble FMS-like tyrosine kinase-1 (s-Flt1) that could affect the thyroid function. In turn, the passage of thyroid hormones and iodine to the fetus is highly regulated within the placental barrier. Together, these mechanisms are hypothesized to contribute to the development of intolerance of thyroid function leading to GHT in a vulnerable individual.

Associations of Hypothyroxinemia With Risk of Preeclampsia-Eclampsia and Gestational Hypertension

OBJECTIVE

To investigate the association between hypothyroxinemia and the risk of preeclampsia-eclampsia and gestational hypertension.

DESIGN

Historical cohort study.

METHODS

The study included pregnant individuals who delivered live-born singletons and had at least one thyroid function assessment during pregnancy at a tertiary hospital. Hypothyroxinemia was defined as thyroid-stimulating hormone (TSH) levels within the normal reference range and free thyroxine (FT4) levels lower than the tenth percentile. Risk ratios (RRs) with 95% confidence intervals (95% CIs) for preeclampsia-eclampsia and gestational hypertension between women with and without a diagnosis of hypothyroxinemia during pregnancy were estimated using a generalized estimating equation model.

RESULTS

A total of 59,463 women with live-born singletons were included in the analysis. Logistic regression models with restricted cubic spline suggested that there was a U-shaped association between FT4 levels and preeclampsia-eclampsia risk. Compared with euthyroid women, those with hypothyroxinemia had an increased risk of preeclampsia-eclampsia (RR = 1.16, 95% CI: 1.02-1.31), and the risk increased with the increasing severity of hypothyroxinemia (p for trend < 0.001). Moreover, persistent hypothyroxinemia from the first to second trimesters was associated with an increased risk of preeclampsia-eclampsia (RR = 1.37, 95% CI: 1.03-1.83), especially for women with severe hypothyroxinemia (RR = 1.70, 95% CI: 1.12-2.58). In contrast, there was no association between hypothyroxinemia and gestational hypertension.

CONCLUSION

Our study suggested that hypothyroxinemia was only associated with an increased risk of preeclampsia-eclampsia, especially in women with persistent hypothyroxinemia in the first half of pregnancy. Analyses of the associated risk of gestational hypertension with hypothyroxinemia were not significant.

Maternal hyperthyroidism and pregnancy outcomes: A population-based cohort study

OBJECTIVE

Maternal hyperthyroidism and antithyroid medications have been associated with adverse pregnancy and perinatal outcomes. This nationwide register-based study investigated the association of maternal hyperthyroidism and antithyroid drug (ATD) use with pregnancy outcomes and included all singleton births in Finland between 2004 and 2013 (N = 571 785).

DESIGN, PATIENTS AND MEASUREMENTS

Hyperthyroid mothers were identified in the Medical Birth Register, and data on ATD use before and/or during pregnancy were collected from the Prescription Register. The odds ratios, with 95% confidence intervals, for adverse outcomes among hyperthyroid mothers and mothers without thyroid disease were compared using logistic regression.

RESULTS

In total, 2144 (0.37%) of all the women had diagnoses of hyperthyroidism, and 580 (27%) of these women had used ATDs before and/or during pregnancy. Compared to the mothers without thyroid disease, maternal hyperthyroidism was associated with older age, multiparity, smoking, previous miscarriages, and overweight or obesity. The mothers diagnosed with hyperthyroidism also had increased odds of gestational hypertensive disorders, caesarean sections, placental abruptions, preterm births, small-for-gestational-age newborns and neonatal intensive care unit treatment. The odds of pregnancy and/or perinatal complications were higher among those who had used ATDs (indicative of active disease), but those who had not received ATD treatment also had increased odds of such complications compared to the mothers without thyroid disease.

CONCLUSIONS

Women with active hyperthyroidism and those with histories of hyperthyroidism should be considered at risk of developing pregnancy and perinatal complications and should therefore be monitored during pregnancy.

Insufficient maternal iodine intake is associated with subfecundity, reduced foetal growth, and adverse pregnancy outcomes in the Norwegian Mother, Father and Child Cohort Study

BACKGROUND

Severe iodine deficiency impacts fertility and reproductive outcomes. The potential effects of mild-to-moderate iodine deficiency are not well known. The aim of this study was to examine whether iodine intake was associated with subfecundity (i.e. > 12 months trying to get pregnant), foetal growth, and adverse pregnancy outcomes in a mild-to-moderately iodine-deficient population.

METHODS

We used the Norwegian Mother, Father and Child Cohort Study (MoBa) and included 78,318 pregnancies with data on iodine intake and pregnancy outcomes. Iodine intake was calculated using an extensive food frequency questionnaire in mid-pregnancy. In addition, urinary iodine concentration was available in a subsample of 2795 pregnancies. Associations were modelled continuously by multivariable regression controlling for a range of confounding factors.

RESULTS

The median iodine intake from food was 121 μg/day and the median urinary iodine was 69 μg/L, confirming mild-to-moderate iodine deficiency. In non-users of iodine supplements (n = 49,187), low iodine intake (< 100-150 μg/day) was associated with increased risk of preeclampsia (aOR = 1.14 (95% CI 1.08, 1.22) at 75 vs. 100 μg/day, p overall < 0.001), preterm delivery before gestational week 37 (aOR = 1.10 (1.04, 1.16) at 75 vs. 100 μg/day, p overall = 0.003), and reduced foetal growth (- 0.08 SD (- 0.10, - 0.06) difference in birth weight z-score at 75 vs. 150 μg/day, p overall < 0.001), but not with early preterm delivery or intrauterine death. In planned pregnancies (n = 56,416), having an iodine intake lower than ~ 100 μg/day was associated with increased prevalence of subfecundity (aOR = 1.05 (1.01, 1.09) at 75 μg/day vs. 100 μg/day, p overall = 0.005). Long-term iodine supplement use (initiated before pregnancy) was associated with increased foetal growth (+ 0.05 SD (0.03, 0.07) on birth weight z-score, p < 0.001) and reduced risk of preeclampsia (aOR 0.85 (0.74, 0.98), p = 0.022), but not with the other adverse pregnancy outcomes. Urinary iodine concentration was not associated with any of the dichotomous outcomes, but positively associated with foetal growth (n = 2795, p overall = 0.017).

CONCLUSIONS

This study shows that a low iodine intake was associated with restricted foetal growth and a higher prevalence of preeclampsia in these mild-to-moderately iodine-deficient women. Results also indicated increased risk of subfecundity and preterm delivery. Initiating iodine supplement use in pregnancy may be too late.

Universal screening for thyroid disease during pregnancy should be performed

Thyroid disease can significantly impact the pregnant woman and her child. Human and animal studies have firmly linked overt hypothyroidism and overt hyperthyroidism to miscarriage, preterm delivery and other adverse pregnancy outcomes. Overt hypothyroidism and overt hyperthyroidism affect 1% of all pregnancies. Treatment is widely available, and if detected early, results in decreased rates of adverse outcomes. Universal screening for thyroid disease in pregnancy can identify patients with thyroid disease requiring treatment, and ultimately decrease rates of complications. Universal screening is cost-effective compared to the currently accepted practice of targeted screening and may even be cost-saving in some healthcare systems. Targeted screening, which is recommended by most professional associations, fails to detect a large proportion of pregnant women with thyroid disease. In fact, an increasing number of providers are performing universal screening for thyroid disease in pregnancy, contrary to society guidelines. Limited evidence concerning the impact of untreated and treated subclinical disease and thyroid autoimmunity has distracted from the core rationale for universal screening - the beneficial impact of detecting and treating overt thyroid disease. Evidence supporting universal screening for overt disease stands independently from that of subclinical and autoimmune disease. The time to initiate universal screening is now.

Safety of antithyroid drugs in pregnancy: update and therapy implications

Introduction: The thionamide antithyroid drugs, methimazole (MMI), its pro-drug derivative carbimazole (CMZ), and propylthiouracil (PTU) are the mainstay of treatment for hyperthyroidism in pregnancy. However, antithyroid drugs carry risks of adverse effects that can affect fetal and maternal well-being.Areas covered: This review provides an update on the safety of antithyroid drugs in pregnancy, focusing on the most serious concerns of severe liver disease and congenital anomalies.Expert opinion: PTU-induced liver disease is uncommon but can run a catastrophic course in pregnancy with a risk of liver failure and threats to maternal or fetal survival. Acute pancreatitis is a relatively rare occurrence that has been linked to thionamide use in a handful of reports in non-pregnant individuals. Observational studies on the risk of birth defects with antithyroid drug exposure in pregnancy overall show an increase in birth defect risk with exposure to CMZ/MMI, and to a lesser extent, PTU. Further studies are required to determine whether the currently recommended approach of switching between thionamide drugs in pregnancy improves outcomes. Ultimately, a preventative strategy of offering definitive therapy to hyperthyroid women of childbearing potential offers the best approach to truly reduce the risks of antithyroid drug adverse effects in pregnancy.

Association between thyroid hormone parameters during early pregnancy and gestational hypertension: a prospective cohort study

Objective

Thyroid dysfunction may play a role in the development of gestational hypertension. However, this relationship remains unclear. This study was performed to evaluate the association between thyroid hormone parameters during early pregnancy and gestational hypertension.

Methods

Women with singleton pregnancies were recruited into this prospective cohort study at 9 to 13 gestational weeks, and their serum thyroid-stimulating hormone, free thyroxine, and free triiodothyronine concentrations were measured using electrochemiluminescence immunoassays. In total, 1226 participants were included in the final analysis.

Results

Of the 1226 participants, 81 subsequently developed gestational hypertension (overall incidence of 6.6%). Compared with women with euthyroidism, both pregnant women with hypothyroidism and those with subclinical hypothyroidism had an increased risk of gestational hypertension (adjusted odds ratio [OR], 3.61; 95% confidence interval [CI], 1.52–8.57 and OR, 2.24; 95% CI, 1.06–4.72, respectively). When the thyroid-stimulating hormone and free thyroxine concentrations were analyzed by quintiles, the women in the highest thyroid-stimulating hormone quintile had a higher risk of gestational hypertension (adjusted OR, 4.22; 95% CI, 1.78–9.05) than the women in the middle quintile.

Conclusion

Our results suggest that hypothyroidism, subclinical hypothyroidism, and a high thyroid-stimulating hormone concentration during early pregnancy are risk factors for gestational hypertension.

Association between thyroid dysfunction and perinatal outcomes in women with gestational hypertension: a retrospective study

Background

Previous studies showed that thyroid dysfunction in women with gestational hypertension could negatively affect maternal and fetal outcomes. In this study, we aimed to investigate whether thyroid dysfunction assessed in the second half trimester contributed to neonatal outcomes of pregnancy in different subtypes of gestational hypertension disease.

Methods

We performed a retrospective case-control study and collected data from 135 singleton pregnant women with gestational hypertension disease and their offspring who delivered in Renmin Hospital of Wuhan University from January 2015 to June 2017. We classified the patients based on the severity of the preeclampsia into three groups: pregnant induced hypertension (PIH), mild preeclampsia (MPE) and severe preeclampsia (SPE). Based on the onset time of preeclampsia, we classified the patients into PIH, early onset preeclampsia (EPE) and late onset preeclampsia. Demographic data and levels of thyroid hormones, as well as the adverse maternal and neonatal outcomes were collected from Electronic Medical Records. Logistic regression was used to estimate the associations between thyroid dysfunction and neonatal outcomes in these patients.

Results

Gestational weeks and neonatal birthweight were significantly lower, while incidence of preterm birth was significantly higher in the SPE and EPE groups than those in the PIH group (P < 0.001). Thyroid dysfunction was more frequent in the SPE group than in the MPE group (P = 0.01). Incidences of both preterm birth and low birth weight were significantly higher in patients with thyroid dysfunction (P = 0.008, P = 0.047 respectively). After adjustment, both severity of gestational hypertension (OR = 4.360, 95%CI [2.050, 9.271], P < 0.001; OR = 4.023, 95%CI [1.933, 8.372], P < 0.001) and thyroid dysfunction (OR = 3.011, 95%CI [1.248, 7.262], P = 0.014; OR = 11.306, 95%CI [1.040, 122.889], P = 0.046) were associated with higher risk of preterm birth and low birth weight, while the onset time of preeclampsia (OR = 0.031, 95%CI [0.009, 0.110], P < 0.001; OR = 0.097, 95%CI [0.033, 0.282], P < 0.001) was negatively associated with the risk of preterm birth and low birth weight.

Conclusion

Severe and early onset preeclampsia, as well as thyroid dysfunction are associated with higher risk of preterm birth and low neonatal birth weight. Therefore, our data suggest that monitoring thyroid hormones in women with preeclampsia might help to predict adverse neonatal outcomes.

Association between thyroid-stimulating hormone and maternal hemodynamics in hypertensive disorders of pregnancy: an observational study

Background

Hypertensive disorders of pregnancy (HDP) are characterized by hemodynamic disturbances. Altered thyroid function is a risk factor for poor outcomes of pregnancy. However, the associations between thyroid function biomarkers and maternal hemodynamics during pregnancy in HDP remain unclear.

Methods

From January 2016 to January 2018, pregnant women diagnosed with HDP admitted to the Nanjing Maternity and Child Health Care Hospital were prospectively enrolled in the third trimester. Normally distributed variables were expressed as mean ± standard deviation and skewed variables were expressed as median (25th percentile, 75th percentile). Correlations between thyroid-stimulating hormone (TSH) or free thyroxine (FT4) and maternal hemodynamic parameters were assessed by Pearson’s correlation coefficient and 95% confidence interval (95%CI). Bonferroni’s correction for multiple correlations was performed. Logistic regression models with odd ratio (OR) and 95%CI were applied to confirm the associations.

Results

A total of 163 third-trimester pregnant women with HDP with a mean gestational age of 35.62 ± 2.83 weeks were recruited. The infant birth weight of patients with elevated TSH levels was lower than that of patients with normal TSH levels (2635 ± 867 g vs. 3037 ± 673 g, p = 0.002). Reduced cardiac output (CO) was defined as CO < 3.5 L/min. The infant birth weight of patients with reduced CO was lower than that of patients with normal CO (2250 ± 510 g vs. 2890 ± 774 g, p = 0.002). TSH levels were significantly and negatively correlated with CO (r = − 0.260, 95%CI: − 0.392- -0.103, p < 0.001). FT4 levels were not significantly correlated with any of the maternal hemodynamic parameters (all p > 0.05). TSH level (OR = 1.371, 95%CI: 1.086–1.733, p = 0.008) was confirmed associated with reduced CO in the logistic regression analysis.

Conclusions

Elevated TSH levels are associated with reduced CO in HDP during the third trimester.

Persistency of Thyroid Dysfunction from Early to Late Pregnancy

Background: Subclinical thyroid disease occurs in approximately 5-8% of all pregnancies and is associated with a higher risk of adverse outcomes such as miscarriage, preterm birth, and suboptimal child neurodevelopment. It is generally assumed that subclinical thyroid disease that persists from early to late pregnancy is associated with a higher risk of adverse outcomes than transient disease. However, it is unknown as to what percentage of women with subclinical disease during early pregnancy have persistent disease in the third trimester. Methods: This study comprised 42,492 mothers for whom early and late pregnancy thyrotropin (TSH), free thyroxine (fT4), triiodothyronine (T3), or TPOAbs were available and who did not receive thyroid treatment before or during pregnancy. We adjusted for potential confounders, including maternal age, parity, anthropometrics, and β-hCG concentrations. Results: Subclinical hypothyroidism and hypothyroxinemia persisted in 24.8% and 17.7% of cases. Overt hyperthyroidism persisted in 8.4% of cases while subclinical hyperthyroidism persisted in 20.9% of cases. Low T3 persisted in 43.4% of cases while elevated T3 persisted in 15.7% of cases. TPOAb positivity persisted in 84.0% of cases. In women with subclinical hypothyroidism, a TSH below ∼5 mU/L at the time of diagnosis was associated with an up to 50% lower risk of persistency. The fT4 concentration at diagnosis predicted hyperthyroidism persistency and TPOAb positivity predicted persistency of all disease entities. Conclusions: Early pregnancy thyroid disease only persists until the third trimester in 8.4-24.8% of cases when left untreated. The main predictor for persistency is TPOAb positivity, with TPOAb-positive women having a lower risk that subclinical hypothyroidism or hypothyroxinemia persists, but a higher risk that (subclinical) hyperthyroidism persists.

Practice Variation in the Care of Subclinical Hypothyroidism During Pregnancy: A National Survey of Physicians in the United States

Evidence regarding the effects of subclinical hypothyroidism (SCH) on adverse pregnancy outcomes and the ability of levothyroxine (LT4) treatment to prevent them is unclear. Available recommendations for the management of SCH during pregnancy are inconsistent. We conducted a nationwide survey among physicians assessing their knowledge of and current practices in the care of SCH in pregnancy and compared these with the most recent American Thyroid Association (ATA) recommendations. In this cross-sectional study, an online survey was sent to active US members of the Endocrine Society. This survey included questions about current practices and clinical scenarios aimed at assessing diagnostic evaluation, initiation of therapy, and follow-up in pregnant women with SCH. In total, 162 physicians completed the survey. ATA guidelines were reviewed by 76%, of whom 53% indicated that these guidelines actually changed their practice. Universal screening was the preferred screening approach (54%), followed by targeted screening (30%). For SCH diagnosis, most respondents (52%) endorsed a TSH level >2.5 mIU/L as a cutoff, whereas 5% endorsed a population-based cutoff as recommended by the ATA. The decision to initiate treatment varied depending on the specific clinical scenario; however, when LT4 was initiated, respondents expected a small/very small reduction in maternofetal complications. In conclusion, despite recently updated guidelines, there is still wide variation in clinical practices regarding the care of women with SCH in pregnancy. Highly reliable randomized trials are required to evaluate the effectiveness of the most uncertain treatment practices on the care of pregnant women with SCH.

Risk of Adverse Obstetric Outcomes and the Abnormal Growth of Offspring in Women with a History of Thyroid Cancer

Background: It is unclear whether a history of thyroid cancer is associated with an increased risk of adverse pregnancy outcomes in subsequent pregnancies. This study aimed to evaluate the risk of adverse obstetric outcomes and the abnormal growth of offspring in women with a history of thyroid cancer. Methods: This retrospective observational study used nationwide data from between 2006 and 2014 to compare pregnancy outcomes of women with a history of thyroid cancer and those with no such history. Cases of thyroid cancer were identified using ICD-10 codes. Results: During the study period, 7232 women with a history of thyroid cancer and 2,269,051 women without a history of thyroid cancer gave birth. The risks of cesarean section, preterm birth, low birth weight, large for gestational age, preeclampsia, placental abruption, placenta previa, and stillbirth were not different between the groups. Women with a history of thyroid cancer had a statistically higher risk of postpartum hemorrhage (odds ratio [OR] = 1.23 [confidence interval (CI) 1.15-1.32], p < 0.05, corrected with the false discovery rate). Additionally, generalized estimating equations analysis showed that there was no difference in the risk of underweight (OR = 1.05 [CI 0.93-1.19]) and obese (OR = 0.94 [CI 0.84-1.05]) offspring assessed over a period of 80 months after adjusting for confounding factors. Conclusions: Women with a history of thyroid cancer have similar pregnancy outcomes and offspring growth to those with no such history.

The impact of isolated maternal hypothyroxinemia during the first and second trimester of gestation on pregnancy outcomes: an intervention and prospective cohort study in China

OBJECTIVES

To explore the effect of isolated maternal hypothyroxinemia (IMH) during the first and second trimester of gestation on pregnancy outcomes. To explore whether levothyroxine (L-T4) treatment of women who had IMH identified in the first trimester improves pregnancy outcomes.

METHODS

Women in the early pregnancy in the iodine-sufficient area (n = 3398) were recruited to this prospective cohort study (ChiCTR-TRC-12002326). Serum thyroid-stimulating hormone (TSH), free thyroxine (FT4), and thyroid peroxidase antibody (TPOAb) were detected. Women with IMH before 12 weeks chose to receive L-T4 or remain untreated. The L-T4 dose was adjusted to attain a normal FT4 and TSH level. Pregnancy outcomes were evaluated during follow-up.

RESULTS

IMH in the first trimester was not associated with increased risk of adverse pregnancy outcome compared with controls. The incidence of macrosomia (p = 0.022) and gestational hypertension (p = 0.018) was significantly higher in IMH identified in the second trimester of gestation compared with controls. IMH identified in the second trimester of gestation was a risk factor for macrosomia [adjusted odds ratio (aOR) 1.942, 95% CI 1.076-3.503, p = 0.027] and gestational hypertension (aOR 4.203, 95% CI 1.611-10.968, p < 0.01), when body mass index in the early pregnancy was < 25 kg/m².

CONCLUSIONS

IMH in the first trimester did not increase the risk of adverse outcomes irrespective of whether women received L-T4 treatment. However, IMH identified in the second trimester was associated with increased risk of adverse pregnancy outcome. The results suggest that thyroid function follow-up during the second trimester is necessary, even if thyroid function is normal during the first trimester.

Impact of subclinical hypothyroidism and thyroid autoimmunity on clinical pregnancy rate after intrauterine insemination in euthyroid women

Objective:

This study aimed to evaluate the association between subclinical hypothyroidism and thyroid autoantibodies with clinical pregnancy rate after intrauterine insemination (IUI) in euthyroid women.

Methods:

In this prospective cohort study, we recruited 497 women who underwent IUI treatment. We assessed thyroid function tests, thyroid antibodies and clinical pregnancy rates of the patients.

Results:

The patients were divided into two groups according to TSH values: normal group, n=387, and subclinical hypothyroidism group 2, n=110. The clinical pregnancy rate was 15.2% in the Control Group and 17.3% in the study group (p=0.656). In the Study Group, 35% of the patients had anti-TPO positivity (p=0.531) and 42.1% of the patients had anti-TG positivity (p=0.285). There was no statistically significant difference in clinical pregnancy rates between the groups in terms of antithyroid antibody positivity (p=0.54; p=0.559, respectively).

Conclusion:

Anti-TPO antibodies and subclinical hypothyroidism had no impact on clinical pregnancy rates in the women submitted to IUI.

Hyperthyroidism in the pregnant woman: Maternal and fetal aspects

Hyperthyroidism during pregnancy is uncommon. Nonetheless, prompt identification and adequate management of hyperthyroidism in a pregnant woman is essential, because uncontrolled thyrotoxicosis significantly increases the risk of maternal and fetal complications. Also, fetal prognosis may be affected by the transplacental passage of maternal thyroid stimulating antibodies or thyrostatic agents, both of which may disrupt fetal thyroid function. Birth defects have been reported in association with the use of antithyroid drugs during early pregnancy. Although rarely, offspring of mothers with Graves’ disease may develop fetal/neonatal hyperthyroidism, the management of which requires a close collaboration between endocrinologists, obstetricians, and neonatologists.

Because of the above considerations, the management of pregnant and lactating women with hyperthyroidism requires special care, bearing in mind that both maternal thyroid excess per se and related treatments may adversely affect the newborn’s health.

In this review we discuss the diagnosis and management of hyperthyroidism in pregnancy, along with the impact of thyrotoxicosis and medications on fetal outcome.

Impact of levothyroxine therapy on obstetric, neonatal and childhood outcomes in women with subclinical hypothyroidism diagnosed in pregnancy: a systematic review and meta-analysis of randomised controlled trials

OBJECTIVE

To determine in women with subclinical hypothyroidism diagnosed in pregnancy whether levothyroxine treatment compared with control, impacts important obstetrical or childhood outcomes (specifically IQ) in randomised controlled trials.

DESIGN

Systematic review and meta-analysis.

STUDY ELIGIBILITY CRITERIA

Randomised trials which met all the following were included: (1) reported original data of women with subclinical hypothyroidism diagnosed in pregnancy (by any prespecified study definition); (2) randomised to either levothyroxine or control (placebo or no treatment); (3) reported obstetrical outcomes and/or childhood neurodevelopmental outcomes and (4) published from 1980 to January 2018 in either English or French language.

DATA SOURCES

Medline, EMBASE, CINAHL, Cochrane Database of Systematic Reviews, Cochrane Central Register of Controlled Trials and ClinicalTrials.gov.

OUTCOME MEASURES

Obstetrical, neonatal and childhood outcomes including: miscarriage, gestational hypertension, pre-eclampsia, preterm delivery, mode of delivery, neonatal intensive care unit admission, birth weight, gestational age at delivery, childhood IQ and neurodevelopmental scores. Risk of bias assessment Cochrane Risk of Bias Tool (Modified) for Quality Assessment of Randomised Controlled Trials RESULTS: Three trials of low to unclear risk of bias with 1837 participants were included. Two studies were meta-analysed for maternal and neonatal outcomes and two studies for childhood IQ. No statistically significant differences were found for any clinical outcomes with levothyroxine therapy compared with control.

LIMITATIONS

Only three trials were identified for inclusion.

CONCLUSIONS

This review, based on three randomised trials in women with subclinical hypothyroidism diagnosed in pregnancy, found no evidence of benefit of levothyroxine therapy on obstetrical, neonatal, childhood IQ or neurodevelopmental outcomes. Current trial evidence does not support the treatment of subclinical hypothyroidism diagnosed in pregnancy.

PROSPERO REGISTRATION NUMBER

CRD4201707980.

Preconception management of thyroid dysfunction

Uncorrected thyroid dysfunction in pregnancy has well-recognized deleterious effects on foetal and maternal health. The early gestation period is one of the critical foetal vulnerability during which maternal thyroid dysfunction may have lasting repercussions. Accordingly, a pragmatic preconception strategy is key for ensuring optimal thyroid disease outcomes in pregnancy. Preconception planning in women with hypothyroidism should pre-empt and mirror the adaptive changes in the thyroid gland by careful levothyroxine dose adjustments to ensure adequate foetal thyroid hormone delivery in pregnancy. In hyperthyroidism, the goal of preconception therapy is to control hyperthyroidism while curtailing the unwanted side effects of foetal and maternal exposure to antithyroid drugs. Thus, pregnancy should be deferred until a stable euthyroid state is achieved, and definitive therapy with radioiodine or surgery should be considered in women with Graves' disease planning future pregnancy. Women with active disease who are imminently trying to conceive should be switched to propylthiouracil either preconception or at conception in order to minimize the risk of birth defects from carbimazole or methimazole exposure. Optimal strategies for women with borderline states of thyroid dysfunction namely subclinical hypothyroidism, isolated hypothyroxinaemia and thyroid autoimmunity remain uncertain due to the dearth of controlled interventional trials. Future trial designs should aspire to recruit and initiate therapy before conception or as early as possible in pregnancy.

Graves' disease and pregnancy

This section deals with the specificities of managing Graves' disease during pregnancy. Graves' disease incurs risks of fetal, neonatal and maternal complications that are rare but may be severe: fetal hyper- or hypothyroidism, usually first showing as fetal goiter, neonatal dysthyroidism, premature birth and pre-eclampsia. Treatment during pregnancy is based on antithyroid drugs alone, without association to levothyroxine. An history of Graves' disease, whether treated radically or not, with persistent maternal anti-TSH-receptor antibodies must be well identified. Fetal monitoring should be initiated in a multidisciplinary framework that should be continued throughout pregnancy. Neonatal monitoring is also crucial if the mother still shows anti-TSH-receptor antibodies at end of pregnancy or underwent antithyroid treatment. The risk of recurrence of hyperthyroidism in the weeks following delivery requires maternal monitoring. The long-term neuropsychological progression of children of mothers with Graves' disease is poorly known.

Thyroid autoantibodies in pregnancy are associated with hypertensive disorders of pregnancy: Ma'anshan Birth Cohort Study

OBJECTIVE

Hypertensive disorders of pregnancy (HDP) have been associated with adverse health outcomes for both mothers and children. Previous studies examining associations of maternal thyroid autoantibodies with HDP indicate conflicting results. The objective of this study was to examine associations of maternal thyroid autoantibody positivity in the first and the second trimesters with the risk of HDP.

DESIGN, PARTICIPANTS AND MEASUREMENTS

In the Ma'anshan Birth Cohort study, a population-based prospective study in China, a total of 3474 pregnant women were enrolled between May 2013 and September 2014. Thyroid autoantibodies, including antithyroperoxidase autoantibody (TPOAb) and antithyroglobulin autoantibody (TgAb), as well as thyroid function tests, were measured in both the first and the second trimesters in 2893 pregnant women. Multivariate logistic regression analyses were conducted to calculate the odds ratio (OR) and 95% confidence interval (CI) for the associations between thyroid autoantibodies and HDP.

RESULTS

Multivariate logistic regression analyses showed that TPOAb positivity in the first trimester was associated with a 1.80 (95% CI = 1.17-2.78) increased odds of HDP after adjustment for confounders, which was mainly due to an increased risk of gestational hypertension (OR = 1.93, 95% CI = 1.17-3.18). In addition, TgAb positivity in the first trimester was associated with a higher risk of HDP (OR = 1.78, 95% CI = 1.16-2.73) after adjustment for confounders, which was mainly due to an increased risk of gestational hypertension (OR = 1.89, 95% CI = 1.15-3.11). These associations were also seen among euthyroid women. Women with positive TPOAb in the second trimester seemed to have a higher risk of gestational hypertension (OR = 1.87, 95% CI = 1.02-3.43) after adjustment for confounders. However, among euthyroid women, TPOAb positivity in the second trimester was not associated with HDP. The TgAb status in the second trimester was not associated with HDP.

CONCLUSIONS

Our results show that TPOAb positivity and TgAb positivity in the first trimester are associated with an increased risk of HDP. These data demonstrate that these associations are even seen among euthyroid women.

Maternal hypothyroxinemia in the first trimester of gestation and association with obstetric and neonatal outcomes and iron deficiency: a prospective Brazilian study

OBJECTIVE

To evaluate the association of isolated hypothyroxinemia in the first trimester with obstetric and neonatal outcomes and iron deficiency.

SUBJECTS AND METHODS

The study was prospective. Women who had become pregnant spontaneously were initially selected. Next, anti-thyroid peroxidase antibodies (TPOAb), free T4 (FT4), total T4 (TT4), TSH, and ferritin were measured. TPOAb-positive women were excluded. The final sample consisted of 596 women with serum TSH between 0.1 and 2.5 mIU/l. Hypothyroxinemia was defined as FT4 < 0.86 ng/dL and < 0.92 ng/dL, corresponding to the 5th and 10th percentiles, respectively, and TT4 < 7.8 ng/dL. None of the pregnant women was treated with levothyroxine until the end of pregnancy.

RESULTS

The women ranged in age from 18 to 36 years, with a median gestation of 9 weeks. T4 levels were not correlated with BMI or maternal TSH. Isolated hypothyroxinemia was observed in 4.3% (FT4 < 0.86 ng/dL), 9% (FT4 < 0.92 ng/dL), and 7% (TT4 < 7.8 ng/dL) of the pregnant women. The frequencies of obstetric and neonatal outcomes were similar in women with versus without hypothyroxinemia. In women without iron deficiency, 8.4%, 3.9%, and 6.5% had FT4 < 0.92 ng/dl, FT4 < 0.86 ng/dL and TT4 < 7.8 ng/dL, respectively. These frequencies of hypothyroxinemia were significantly higher among women with iron deficiency (20.7%, 14.8% and 17.2%, respectively).

CONCLUSIONS

This prospective Brazilian study found no association between isolated hypothyroxinemia in the first trimester of gestation and obstetric or neonatal outcomes, but an association was demonstrated with iron deficiency.

Associations of maternal iodine status and thyroid function with adverse pregnancy outcomes in Henan Province of China

OBJECTIVE

The study aimed to explore the effects of maternal iodine status and thyroid diseases on adverse pregnancy outcomes.

METHODS

A prospective study was conducted on 2347 pregnant women, who provided 2347 urinary samples tested for iodine, 1082 serum samples tested for thyroid function, and 2347 questionnaires about demographic information. Their pregnancy outcomes were recorded and compared between different urinary iodine concentration (UIC) and thyroid function groups.

RESULTS

Pregnant women with UIC between 150 and 249 μg/L had lower incidences of preeclampsia (adjusted odds ratio (OR) 0.12, 95% CI: 0.01-0.87), placenta previa (adjusted OR 0.06, 95% CI: 0.01-0.69) and fetal distress (adjusted OR 0.10, 95% CI: 0.02-0.64) than the reference group (UIC < 50 μg/L). Women with UIC between 100 and 149 μg/L had lower risks of abnormal amniotic fluid (adjusted OR 0.32, 95% CI: 0.12-0.87) and fetal distress (adjusted OR 0.08, 95% CI: 0.01-0.82). Women with UIC above 249 μg/L had a significant higher rate of abnormal amniotic fluid (adjusted OR 0.38, 95% CI: 0.16-0.89). Clinical and subclinical hypothyroidism during pregnancy increased the risk of preterm delivery by 4.4 times (P = 0.009) and 3.0 times (P =  0.014), respectively. Isolated hypothyroxinemia had increased odds of having macrosomia (adjusted OR 2.22, 95% CI: 1.13-4.85). Clinical hyperthyroidism was significantly associated with miscarriage (adjusted OR 2.12, 95% CI: 1.92-96.67) and fetal distress (adjusted OR 9.53, 95% CI: 1.05--81.81). Subclinical hyperthyroidism had a significant association with umbilical cord entanglement (adjusted OR 3.82, 95% CI: 1.38-10.58). Isolated hyperthyroxinemia was associated with preterm delivery (adjusted OR 4.73, 95% CI: 1.49-15.05).

CONCLUSIONS

Maternal iodine status and thyroid diseases during pregnancy were associated with adverse pregnancy outcomes.

Management of Subclinical Hypothyroidism in Pregnancy: A Comment from the Italian Society of Endocrinology and the Italian Thyroid Association to the 2017 American Thyroid Association Guidelines-"The Italian Way"

The 2017 American Thyroid Association guidelines for the diagnosis and management of thyroid disease during pregnancy and the postpartum were published six years after the previous ones. They provide comprehensive clinical recommendations for the whole spectrum of thyroid diseases, as well as for optimal iodine intake during pregnancy, postpartum, and lactation. The present position statement mainly regards the recommended flow chart for therapeutic decision making in pregnant women being diagnosed with subclinical hypothyroidism. Here, we comment on the major biochemical and clinical situations and the corresponding therapeutic recommendations. In particular, we welcome the critical revision of the thyrotropin (TSH) reference range in pregnancy, and we agree that there is no need to treat thyroid peroxidase antibody-negative women with a serum TSH ranging from 2.5 μIU/mL to the upper limit of the reference range. This recommendation will hopefully reduce the huge proportion of healthy pregnant women in whom, according to the previous guidelines, levothyroxine therapy had to be initiated. On the other hand, we are concerned with the recommendation to only "consider treatment" in thyroid peroxidase antibody-negative pregnant women with a serum TSH ranging from the upper limit of the reference range to 10.0 μIU/mL. This is because thyroid antibodies may be falsely negative during gestation, and serum negative chronic autoimmune thyroiditis is a well-known clinical entity even outside pregnancy. Based on these and other arguments, we recommend treatment with levothyroxine in pregnant women with TSH levels ranging between the upper limit of the reference range and 10.0 μIU/mL independently from their thyroid antibody status.

Effect of Iodine Nutrition on Pregnancy Outcomes in an Iodine-Sufficient Area in China

Many studies focused on the association between thyroid disease and pregnancy outcomes. The present study explored the effect of iodine nutrition during the first trimester on pregnancy outcomes. One thousand five hundred sixty-nine pregnant, euthyroid women at ≤12 weeks of gestation in an iodine-sufficient area in China were recruited. According to the World Health Organization (WHO) criteria for iodine nutrition during pregnancy, participants were divided into four groups: adequate iodine (median urinary iodine concentration (UIC), 150-249 μg/L), mild deficiency (UIC, 100-150 μg/L), moderate and severe deficiency (UIC, <100 μg/L), and more than adequate and excessive (UIC, ≥250 μg/L) groups. Pregnancy outcomes, including abortion, gestational hypertension, pre-eclampsia, gestational diabetes mellitus (GDM), placenta previa, placental abruption, preterm labor, low birth weight infants, macrosomia, breech presentation, and cord entanglement, were obtained during follow-up. The results showed that there was no significant difference in general characteristics, including age, body mass index, abdominal circumference, systolic blood pressure, diastolic blood pressure, heart rate, smoking rate, and drinking rate, among the four groups. In the more than adequate and excessive group, thyroid-stimulating hormone (TSH) was greater and free thyroxine (FT4) was lower than any other groups but still within normal range. The thyroglobulin (Tg) level was greater in the moderate and severe deficiency group. The incidence of GDM was significantly greater in women with mild iodine deficiency than in women with adequate iodine nutriture (18.38 vs. 13.70%, p < 0.05). Compared with the adequate group, incidence of macrosomia was significantly greater in the more than adequate and excessive group (12.42 vs. 9.79%, p < 0.05). Mild iodine deficiency was an independent risk factor for GDM (odds ratio = 1.566, 95% confidence interval = 1.060-2.313, p = 0.024); more than adequate and excessive iodine was an independent risk factor for macrosomia (OR = 1.917, CI = 1.128-3.256, p = 0.016). In summary, during 1st trimester, both mild iodine deficiency and excessive iodine intake had adverse impacts on pregnancy outcomes in an iodine-sufficient area.

The association of maternal thyroid function with placental hemodynamics

STUDY QUESTION

What is the clinical association of maternal thyroid function with placental hemodynamic function?

SUMMARY ANSWER

A higher free thyroxine (FT4) concentration in early pregnancy is associated with higher placental vascular resistance.

WHAT IS KNOWN ALREADY

Suboptimal placental function is associated with preeclampsia (which, in turn, further deteriorates placental hemodynamics and impairs the fetal blood supply), fetal growth restriction and premature delivery. Studies have suggested that thyroid hormone (TH) has a role in placental development through effects on trophoblast proliferation and invasion.

STUDY DESIGN, SIZE, DURATION

This study was embedded in The Generation R cohort, a population-based prospective study from early fetal life onwards in Rotterdam, the Netherlands. In total, 7069 mothers with expected delivery date between April 2002 and January 2006 were enrolled during early pregnancy.

PARTICIPANTS/MATERIALS, SETTING, METHOD

Thyroid-stimulating hormone (TSH) and free thyroxine (FT4) concentrations were measured during early pregnancy (median 13.4 weeks, 95% range 9.7-17.6 weeks). Placental function was assessed by Doppler ultrasound via measurement of arterial vascular resistance, i.e. umbilical artery pulsatility index (PI) and uterine artery resistance index (RI) (both measured twice, between 18-25th and after 25th gestational weeks) and the presence of uterine artery notching (once after the 25th gestational week) in 5184 pregnant women.

MAIN RESULTS AND THE ROLE OF CHANCE

FT4 was positively linearly associated with umbilical artery PI in the second and third trimesters as well as with uterine artery RI in the second trimester and the risk of uterine artery notching in the third trimester (P < 0.05 for all). The association of thyroid function with preeclampsia and birth weight was partially mediated through changes in placental function, with the percentages of mediated effects being 10.4% and 12.5%, respectively.

LIMITATIONS, REASONS FOR CAUTION

A potential limitation is the availability of only a single time point for TH measurements and different numbers of missing placental ultrasound measurements for the adverse outcomes.

WIDER IMPLICATIONS OF THE FINDINGS

A higher FT4 concentration in early pregnancy is associated with higher vascular resistance in the second and third trimesters in both the maternal and fetal placental compartment. These effects on placental function might explain the association of FT4 with adverse pregnancy outcomes, including preeclampsia and fetal growth restriction.

STUDY FUNDING/COMPETING INTEREST(S)

This work was supported by a fellowship from ERAWEB, a project funded by the European Commission (to M.B.) and by clinical fellowship from The Netherlands Organization for Health Research and Development (ZonMw), Project 90700412 (to R.P.P.). The authors have no conflict of interest.

TRIAL REGISTRATION NUMBER

N/A.

Maternal thyroid function, prepregnancy obesity and gestational weight gain-The Generation R Study: A prospective cohort study

OBJECTIVE

Maternal prepregnancy obesity and excessive gestational weight gain are associated with pregnancy complications. Thyroid function is related to differences in body mass index (BMI) in adult populations. We examined the associations of maternal thyroid function in early pregnancy with maternal BMI and weight gain during pregnancy.

DESIGN AND METHODS

In a population-based prospective cohort study among 5726 mothers, we measured maternal TSH and FT4 levels at 13.5 weeks of gestation (95% range: 9.7-17.6 weeks). Maternal weight was assessed before pregnancy and in each trimester.

RESULTS

Higher maternal TSH levels were associated with higher prepregnancy BMI (difference: 0.18 kg/m² [95% CI: 0.01, 0.36] per SD increase in maternal TSH level) and higher total gestational weight gain (difference: 0.02 kg/wk [95% CI: 0.01, 0.03] per SD increase in maternal TSH level). Higher maternal FT4 levels were associated with lower prepregnancy BMI (difference: -0.44 kg/m² [95% CI: -0.63, -0.26] per SD increase in maternal FT4 level) and lower total gestational weight gain (difference: -0.01 kg/wk [95% CI: -0.02, -0.01] per SD increase in maternal FT4 level). The associations of maternal thyroid function with weight gain in early pregnancy were stronger than those with weight gain in mid and late-pregnancy. Maternal hypothyroidism was associated with higher prepregnancy BMI and early pregnancy weight gain, whereas opposite effects were observed for maternal hyperthyroidism (P<.05).

CONCLUSIONS

Higher maternal TSH level and lower FT4 level in early pregnancy are associated with higher prepregnancy BMI and higher gestational weight gain. Further studies are needed to explore maternal and foetal consequences.

Thyroid disease in pregnancy: new insights in diagnosis and clinical management

Adequate thyroid hormone availability is important for an uncomplicated pregnancy and optimal fetal growth and development. Overt thyroid disease is associated with a wide range of adverse obstetric and child development outcomes. An increasing number of studies now indicate that milder forms of thyroid dysfunction are also associated with these adverse pregnancy outcomes. The definitions of both overt and subclinical thyroid dysfunction have changed considerably over the past few years, as new data indicate that the commonly used fixed upper limits of 2.5 mU/l or 3.0 mU/l for thyroid-stimulating hormone (TSH) are too low to define an abnormal thyroid function. Furthermore, some studies now show that the reference ranges are not necessarily the best cut-off for identifying pregnancies at high risk of adverse outcomes. In addition, data suggest that thyroid peroxidase autoantibody positivity and high or low concentrations of human chorionic gonadotropin seem to have a more prominent role in the interpretation of thyroid dysfunction than previously thought. Data on the effects of thyroid disease treatment are lacking, but some studies indicate that clinicians should be aware of the potential for overtreatment with levothyroxine. Here, we put studies from the past decade on reference ranges for TSH, determinants of thyroid dysfunction, risks of adverse outcomes and options for treatment into perspective. In addition, we provide an overview of the current views on thyroid physiology during pregnancy and discuss strategies to identify high-risk individuals who might benefit from levothyroxine treatment.

Maternal low thyroxin levels are associated with adverse pregnancy outcomes in a Chinese population

Although thyroid dysfunction in early pregnancy may have adverse effects on pregnancy outcomes, few studies have examined the relationship between maternal low free thyroxin (FT4) levels in both first and third trimesters of pregnancy and the incidence of adverse pregnancy outcomes. We hypothesized that low FT4 levels in either first or third trimesters of pregnancy may have different effects on pregnancy outcomes. The study included 6,031 mothers who provided both first and third pregnancy serum samples for analyses of thyroid function. Adverse pregnancy outcomes, such as gestational diabetes mellitus (GDM), pregnancy-induced hypertension and preeclampsia, were diagnosed using the oral glucose tolerance test, blood pressure and urine protein test. Serum metabolites like adenosine and its analogues were identified using hydrophilic interaction liquid chromatography (HILIC)-tandem mass spectrometry (MS/MS). The incidence of hypothyroidism in pregnant women tended to increase with age and pre-pregnancy body mass index (BMI). The incidence of GDM was negatively correlated with maternal FT4 levels during early pregnancy while the incidence of preeclampsia was negatively correlated with maternal FT4 levels during late pregnancy. The incidence of pregnancy-induced hypertension was not significantly correlated with maternal FT4 levels. The women who had isolated maternal hypothyroxemia (IMH) in the third trimester of pregnancy had an increased risk of developing preeclampsia. Some metabolites like adenosine and its analogues in the serum were significantly changed in pregnant mothers with IMH. In conclusion, low FT4 levels during pregnancy are a risk factor for GDM and preeclampsia. Adenosine and its analogues may be important bridges between IMH and preeclampsia.

The Emerging Role of Epigenetics in Autoimmune Thyroid Diseases

Autoimmune thyroid diseases (AITD) are a group of both B cell- and T cell-mediated organ-specific autoimmune diseases. Graves’ disease and Hashimoto thyroiditis are the two main clinical presentations of AITD. Both genetic and environmental factors have important roles in the development of AITD. Epigenetics have been considered to exert key roles in integrating those genetic and environmental factors, and epigenetic modifications caused by environmental factors may drive genetically susceptibility individuals to develop AITD. Recent studies on the epigenetics of AITD have provided some novel insights into the pathogenesis of AITD. The aim of this review is to provide an overview of recent advances in the epigenetic mechanisms of AITD, such as DNA methylation, histone modifications, and non-coding RNAs. This review highlights the key roles of epigenetics in the pathogenesis of AITD and potential clinical utility. However, the epigenetic roles in AITD are still not fully elucidated, and more researches are needed to provide further deeper insights into the roles of epigenetics in AITD and to uncover new therapeutic targets. Although there are many studies assessing the epigenetic modifications in AITD patients, the clinical utility of epigenetics in AITD remains poorly defined. More studies are needed to identify the underlying epigenetic modifications that can contribute to accurate diagnosis of AITD, adequate choice of treatment approach, and precise prediction of treatment outcomes.

First trimester isolated maternal hypothyroxinaemia: adverse maternal metabolic profile and impact on the obstetrical outcome

BACKGROUND

Isolated maternal hypothyroxinaemia (IH) is defined as low maternal FT4 (<5th percentile) and normal thyroid-stimulating hormone. There is concern on its potential negative effects on the mother and offspring.

OBJECTIVE

We aimed to evaluate the prevalence of IH and to assess the consequences of hypothyroxinaemia on the maternal and foetal outcomes.

SUBJECTS AND METHODS

From a total of 1300 consecutive pregnant women recruited during the prenatal screen (mean gestational age, 11·8 weeks), thyroid function parameters were assessed in 879 women. After exclusion of women with T4 supplements, with twin pregnancies and with diabetes, data from 783 women were included. Maternal and neonatal outcomes in 55 selected women with IH and negative thyroid auto-antibodies without thyroid disorders or pregnancy achieved through assisted reproductive techniques were compared with a selected euthyroid control group (N = 165).

RESULTS

Among the 783 non diabetic singleton pregnant women, 68 women (8·7%) were identified with IH. When compared to the selected euthyroid controls, selected women with hypothyroxinaemia had significantly increased body mass index (BMI) in preconception (P = 0·003), in the first trimester (P = 0·004) and at the time of delivery (P = 0·001). At term, foetal breech presentation and caesarean section rate were significantly higher (P = 0·006 and P = 0·026, respectively) than in the euthyroid controls. A significant increase in macrosomia was also noted (P = 0·026).

CONCLUSION

The prevalence of hypothyroxinaemia in early pregnancy was of 8·7%. IH is associated with an increased maternal BMI and is related with a risk of breech presentation, a significant increase in macrosomia and caesarean sections. Screening should consider overweight as risk factor for hypothyroxinaemia.

Stimulation of Thyroid Function by Human Chorionic Gonadotropin During Pregnancy: A Risk Factor for Thyroid Disease and a Mechanism for Known Risk Factors

BACKGROUND

Thyroid autoimmunity is a major risk factor for gestational thyroid disease, and recently various other risk factors have been identified, including maternal age, body mass index (BMI) and parity. Human chorionic gonadotropin (hCG) is an important determinant of gestational thyroid function, yet it is unknown to what extent differences in hCG concentration affect the risk for thyroid disease. We have recently shown that thyroperoxidase antibody positivity impairs the thyroidal response to hCG stimulation, which may suggest that this is a mechanism through which thyroid autoimmunity acts as a risk factor for thyroid disease.

OBJECTIVE

The purpose of this study is to determine whether hCG is a risk factor for thyroid disease entities and whether recently identified risk factors for thyroid disease may influence the thyroidal response to hCG stimulation.

METHODS

Human chorionic gonadotropin, thyrotropin (TSH), and free thyroxine (FT4) were measured in 5435 pregnant women participating in a prospective cohort. The association of hCG with thyroid disease entities, and the association of known risk factors with thyroidal response to hCG stimulation were studied using multivariable linear regression models.

RESULTS

Higher hCG concentrations were associated with a higher risk of subclinical and overt hyperthyroidism. Lower hCG concentrations were associated with a higher risk of hypothyroxinemia. In contrast, hCG concentrations were not associated with subclinical hypothyroidism. Further analyses showed that in women with hypothyroxinemia, high hCG concentrations still suppressed TSH. However, in women with subclinical hypothyroidism, high hCG concentrations were not associated with higher FT4. Higher BMI, male fetal sex, and maternal parity >2 were associated with a lower thyroidal response to hCG stimulation.

CONCLUSIONS

Human chorionic gonadotropin is associated with the risk of (subclinical) hyperthyroidism and hypothyroxinemia, but not with the risk of (subclinical) hypothyroidism. Women with hypothyroxinemia have a normal response to thyroidal stimulation by hCG, but this was abnormal in women with subclinical hypothyroidism. Known risk factors for thyroid dysfunction (BMI and parity), and also male fetal sex, are associated with a lower thyroidal response to hCG stimulation.