The most controversial issue in the field of thyroid and pregnancy is whether clinicians should screen all pregnant women for thyroid disease, and if so, should the screening be performed before pregnancy or at the first prenatal visit. Considering the uncertainties surrounding the beneficial effects of treating subclinical hypothyroidism on adverse maternal and fetal outcomes, well-known international societies now believe that generalized screening is not mandatory based on current evidence. They recommend just selective screening of women at high risk of thyroid disease (1,2).
Although majority of criteria for screening of thyroid diseases during pregnancy is fulfilled based on the Wilson and Jungner criteria for disease screening (3), controversy regarding some criteria still exists. There is a dilemma over universal screening and selective screening of women at high risk of thyroid dysfunction before and during pregnancy that remains unresolved. One of the screening criteria is that the treatment must be effective; until today we do not have firm data for the efficacy of treatment in subclinical hypothyroidism detected during screening programs. Additionally, the cost effectiveness of general screening is a major issue that needs to be discussed and resolved based on the socio-economic status and medical budget of each country. Health organizations are required to set priorities and allocate resources within the constraint of limited funding for each disease; it seems that screening strategies need to be individualized for each country. The American Association of Clinical Endocrinologists (AACE), American Thyroid Association (ATA), Endocrine Society and American College of Obstetrics and Gynecology (ACOG) do not recommend universal thyroid assessment for every pregnant woman, and suggest the targeted high-risk case finding approach (1,2,4,5). The 2011 ATA pregnancy guidelines (6) recommended screening in high risk groups, a recommendation which has not changed over the past 6 years, i.e., is the same in the 2017 ATA pregnancy guidelines (1). These guidelines underscore the criteria mentioned above, i.e., the cost effectiveness and the practicality/feasibility of the screening approach. Studies evaluating the question of “to screen or not to screen for thyroid dysfunction during pregnancy” demonstrate mixed conclusions. Several ongoing investigations and future studies will shed further light on this controversial topic.
Recently since associations between thyroid dysfunction in terms of hypo- and hyperthyroidism, thyroid autoimmunity and adverse pregnancy outcomes (maternal, fetal and neonatal) have become more evident, this has led to increased scientific debate on the advisability of universal thyroid screening.
This review aims to discuss updates on the important issue of thyroid screening during pregnancy and to highlight the gap in evidence that has led to the controversies on this topic.
The terms “screening” AND “thyroid” AND “pregnancy” were used to search Medline for English-language papers published from 1990 to the end of January 2018; a combination of more general search term usage with additional filtering of articles was applied to include all relevant articles. We limited our search results considering observational studies, clinical trials, review articles, meta-analyses and guidelines of major international organizations. After reviewing of titles of 482 articles by two endocrinologists, the articles were divided into 4 broad categories: (I) those that covered screening of thyroid disorders during pregnancy, (II) observational studies that addressed consequences of untreated thyroid disorders and/or thyroid autoimmunity during pregnancy in terms of pregnancy, fetal, neonatal and offspring outcomes, (III) articles the main focus of which were the effects of treatment of subclinical hypothyroidism on pregnancy outcomes, and (IV) the ones that discussed effects of treatment of subclinical hypothyroidism on fetal and offspring outcomes. Finally, we focused on high quality and important studies. As a shortcoming of each narrative review, selection bias cannot be excluded.
Thyroid dysfunction will be missed when the case-finding screening approach is implemented
Thyroid dysfunction is a common occurrence in pregnancy and affects both maternal and fetal outcomes. It seems that targeted thyroid screening is not efficient in identifying women at risk of thyroid dysfunction; here we do not discuss subclinical or overt hyperthyroidism as the former usually has no adverse clinical consequences during pregnancy and the latter usually occurs with obvious signs and symptoms that would not be missed in clinical practice.
In a recent study by Hosseini et al., incidence of subclinical hypothyroidism was reported to be similar among women with risk factors for hypothyroidism and those without these risk factors and targeted screening were shown to miss 10% of women with hypothyroidism (7). A cross-sectional prospective study conducted on 1,600 Iranian pregnant women in their first trimester of pregnancy found that the targeted high-risk case finding approach overlooked about one-third of pregnant women with thyroid dysfunction (8). Vaidya et al. (9) reported that by using the targeted high-risk case finding approach, about 30% of women with hypothyroidism went undetected. A study of pregnant women in Boston metropolitan area found that 80.4% of pregnant women with TSH elevation would have been missed based on current high-risk screening guidelines (10).
Overall, 1% of pregnant women suffer from overt hypothyroidism that had been present before conception; in such cases, adverse pregnancy outcomes are almost inevitable and treatment of overt thyroid disease decreases maternal and fetal morbidity and mortality (11) and is cost effective (12,13). Even women planning a pregnancy within 6 months should be regarded as having a ‘pregnant status’ and need to be followed more closely, because preconception TSH elevation is reported to be associated with increased risk of adverse pregnancy outcomes, even if the values are within the normal non-pregnant range (14).
Consequences of missing overt thyroid dysfunction during pregnancy
It is established that both overt hypothyroidism and overt hyperthyroidism lead to adverse pregnancy outcomes and must be treated (15-17). Many observational studies showed that maternal hypothyroidism, both overt and subclinical, are strongly associated with preterm birth, low birth weight, reduced head circumference growth in infants, placental abruption, gestational hypertension, gestational diabetes, cognitive delay and many other abnormal neurobehavioral problems of exposed offspring (16,18-20). No prospective, randomized clinical trial of levothyroxine on preventing adverse pregnancy outcomes has been designed, because it is considered unethical to design such study in overt hypothyroid mothers. Therefore, the current consensus is that all overt thyroid disorders must be treated during pregnancy.
Consequences of missing subclinical thyroid dysfunction during pregnancy
The question that remains unanswered is: “What are the benefits, if any, of treating subclinical hypothyroidism during pregnancy”. There are relatively few well-designed randomized clinical trials available aimed at answering this question.
Subclinical hypothyroidism and pregnancy outcomes
The impact of subclinical hypothyroidism on pregnancy outcomes remains controversial. While some observational studies showed subclinical hypothyroidism increases adverse pregnancy outcomes such as preterm labor, miscarriage, gestational hypertension, placental abruption, fetal distress, preeclampsia and gestational diabetes (21,22), others reported no significant associations (23).
Thyroid autoimmunity and pregnancy outcomes
Laboratory tests of thyroid autoantibodies are now available worldwide. Thyroid antibody
Effects of levothyroxine treatment of subclinical hypothyroidism on pregnancy outcomes
Results of studies that focused on treatment with regard to thyroid autoimmunity were not encouraging. A prospective randomized trial assessing the impact of LT4 in euthyroid pregnant women with TSH levels between 0.5 and 2.5 mIU/L and autoimmune thyroid disease showed no impact of therapy on the rate of miscarriage and preterm delivery (30). Other studies showed that euthyroid, TPOAb positive women treated with LT4 and euthyroid TPOAb negative women displayed a lower rate of preterm deliveries compared with euthyroid, TPOAb positive women who were not treated with levothyroxine (31,32).
Negro et al. demonstrated that the treatment of thyroid dysfunction detected by universal screening prevented adverse outcomes in pregnant women (33); they also showed that euthyroid TPOAb positive women who received levothyroxine (LT4) had a significant reduction in preterm deliveries (from 22% to 7%) and miscarriage rates (from 14% to 3.5%) (31). In a recent study, it was shown that LT4 could decrease preterm delivery in TPOAb negative women with TSH values ≥4.0 mIU/L (34). Findings of the Thyroid AntiBodies and LEvoThyroxine (TABLET) study, aimed to investigate whether taking a small (50 µg) dose of LT4 by TPOAb positive euthyroid women before and during pregnancy will decrease the rate of miscarriage and preterm delivery (ISRCTN15948785, https://doi.org/10.1186/ISRCTN15948785), have not yet been published.
Fetal and offspring outcomes in subclinical hypothyroidism
The effect of subclinical hypothyroidism on cognitive function and neurodevelopmental aspects of fetus and offspring remains controversial.
A prospective observational study from Netherlands reported that the mean mental developmental index score at the age of 6 and 12 months was 16 points lower for infants who were born to mother with subclinical hypothyroidism compared to those born to euthyroid pregnant women (35). Findings of the Li et al. study showed children aged 25–30 months of women with subclinical hypothyroidism at 16–20 weeks of gestation, had mean intelligence scores (8.88 points) and mean motor scores (9.98 points) lower than those of the control group; increased maternal serum TSH, decreased maternal serum FT4, and elevated maternal TPOAb titers were associated with lower intelligence scores (ORs 15.63, 12.98, and 6.69, respectively) and poorer motor scores (ORs 9.23, 5.52, and 8.25, respectively) (36). In a recent prospective cohort study from Netherlands, maternal TSH concentrations in 9–18 weeks of pregnancy were not associated with child IQ evaluated at a median of 6 years of age (37).
Effects of levothyroxine treatment of subclinical hypothyroidism on the fetus and offspring
The Stagnaro-Green et al. study consisting of two prospective randomized trials assessing the impact of levothyroxine on offspring IQ in women with subclinical hypothyroidism with TSH values ≥2.5 mIU/L or isolated hypothyroxinemia, found no significant effect (38).
It has been suggested that subclinical hypothyroidism during pregnancy is associated with impaired cognitive development in offspring and treatment may improve neurocognitive outcomes. However, data available from RCTs does not support this hypothesis. Lazarus et al., conducted a well-designed randomized controlled trial (RCT) of pregnant women (gestation approximately 16 weeks) to find the treatment effect on intelligence quotient (IQ) at 3 years of age in children; women were assigned to a screening and a control group; all positive screening women were prescribed 150 µg of LT4 per day; they showed that antenatal screening and maternal treatment for hypothyroidism did not result in improved cognitive function in children at 3 years of age, as the mean IQ and the proportion of children with IQ levels below 85 did not differ significantly between the children of the mothers treated during pregnancy and the children of those who were not treated (39). Results of “the second wave of the Controlled Antenatal Thyroid Screening (CATS II) study” (40) have recently been released (41); IQ at age of 9.5 years of children of 119 LT4-treated and 98 untreated mothers with subclinical thyroid dysfunction during their pregnancy was compared to that of children of 232 mothers with normal gestational thyroid function. Maternal LT4 treatment was not associated with neurocognitive improvement of offspring at age of 9.5. Another RCT by Casey et al. was conducted on 677 women with subclinical hypothyroidism and 526 ones with hypothyroxinemia who underwent randomization at a mean of 16.7 and 17.8 weeks of gestation, respectively; in this study, treatment for subclinical hypothyroidism or hypothyroxinemia, initiated in 8–20 weeks of gestation did not result in significantly better cognitive outcomes in children through 5 years of age, compared to outcomes in those who had received no treatment for the conditions (42).
The main shortcoming of above-mentioned trials is that LT4 treatment has been initiated late at the second trimester of pregnancy when fetal thyroid development and thyroid hormone synthesis and secretion have nearly been completed (43).
Cost-effectiveness of universal versus case-finding screening methods
A decision-analytic model that compared the incremental cost per quality-adjusted life-year (QALY) gained among those who underwent universal screening or categorized to high-risk screening group versus the no screening one documented that risk-based screening and universal screening were both cost-effective relative to no screening, with incremental cost-effectiveness ratios (ICERs) of $6,753/QALY and $7,138/QALY, respectively. Also universal screening was cost-effective, compared to the case finding strategy (12); results of other cost-effectiveness studies were concordant with this finding (13,44). Overall, it appears that studies tend to support universal screening in terms of cost-effectiveness.
The reasons behind controversies in screening strategies
The Wilson criteria for disease screening emphasize the important features of any screening program, as shown in Table 1. There is a dilemma between universal screening and selective screening of women at high risk of thyroid dysfunction during pregnancy that has remained unresolved. One of the criteria is that treatment should be more effective if initiated early.
Since a higher percentage of thyroid dysfunction in pregnant women is in the form of subclinical hypothyroidism, and given the lack of clear data for efficacy of treatment, there is ongoing controversy/debate regarding the need for universal screening for thyroid dysfunction during pregnancy versus a case-finding approach (1,45). This could be due to flaws in study design regarding the study population, definition of subclinical hypothyroidism- with different biochemical cut-offs, thyroid autoimmunity, time of recruitment of pregnant women and the time of follow-up. Additionally, it seems that cost-effectiveness of screening programs is still under question that should be taken into account for each country individually. Health policy makers should choose the most cost-effective screening method for public health programs for each specific population based on their guaranteed maximum price. In many countries in the world, where their gross national product (GNP) and health budgets are low, screening of diseases such as thyroid diseases in pregnancy may not be a priority in health matters.
Areas of uncertainty
Studies have been hindered by the limited data available regarding assessment of thyroid function during early pregnancy. More studies are needed to evaluate the benefits of thyroid screening and treatment before and/or in early pregnancy. So far studies conducted for evaluation of levothyroxine effects in pregnancy have used protocols where levothyroxine treatment is initiated only at the end of the first trimester or later (39,42). Further studies should consider this issue at the design stage and evaluate the effect of treatment as early as possible. In addition, limited studies have evaluated the relationship between preconception thyroid hormone levels and pregnancy outcomes; a secondary analysis of a prospective cohort of 18–40-year-old women with 1–2 previous pregnancy losses, showed that subclinical hypothyroidism and thyroid autoimmunity were not associated with an increased risk of preterm delivery, gestational diabetes mellitus, or preeclampsia (46).
More evidence is required to assess the benefits/advantages and disadvantages of the two different screening strategies for thyroid dysfunction before and during pregnancy, looking for maternal, neonatal and offspring’s health outcomes. We also need to know how the diagnosis of subclinical hypothyroidism could affect quality of life during pregnancy. Overall, it seems that the time has come for universal screening for thyroid disorders during and even before pregnancy. A thyroid screening program during pregnancy should be based on systematic evaluation of several factors, including the burden of the thyroid disorders in pregnant women, the cost effectiveness of the screening intervention, and how well a given screening test performs in the target population; its performance can be judged by how many individuals must be screened to prevent one pregnancy complication, balanced with how many pregnant women who undergo screening have a positive or abnormal test result when the treatment has no effect (false-positive test). The number of individuals with positive results who actually proceed to follow-up and receive treatment is a critical issue to consider for pregnant mothers. Finally, screening strategies need to be individualized for each country according to disease burden, case finding costs and available health services.
We wish to acknowledge Ms. Niloofar Shiva for critical editing of English grammar and syntax of the manuscript.
Conflicts of Interest: The authors have no conflicts of interest to declare.
- Alexander EK, Pearce EN, Brent GA, et al. 2017 Guidelines of the American Thyroid Association for the Diagnosis and Management of Thyroid Disease During Pregnancy and the Postpartum. Thyroid 2017;27:315-89. [Crossref] [PubMed]
- Davies TF. The ATA, the Endocrine Society, and AACE confuse endocrinologists on thyroid disease in pregnancy. American Thyroid Association. American Association of Clinical Endocrinology. Thyroid 2000;10:107. [Crossref] [PubMed]
- Wilson JM, Jungner G. Principles and practice of screening for disease. 1968. Available online: http://www.who.int/iris/handle/10665/37650
- American College of Obstetrics and Gynecology. ACOG practice bulletin. Thyroid disease in pregnancy. Number 37, August 2002. American College of Obstetrics and Gynecology. Int J Gynaecol Obstet 2002;79:171-80. [Crossref] [PubMed]
- De Groot L, Abalovich M, Alexander EK, et al. Management of thyroid dysfunction during pregnancy and postpartum: an Endocrine Society clinical practice guideline. J Clin Endocrinol Metab 2012;97:2543-65. [Crossref] [PubMed]
- Stagnaro-Green A, Abalovich M, Alexander E, et al. Guidelines of the American Thyroid Association for the diagnosis and management of thyroid disease during pregnancy and postpartum. Thyroid 2011;21:1081-125. [Crossref] [PubMed]
- Akram FH, Johansson B, Möllerström G, et al. Incidence of Subclinical Hypothyroidism and Hypothyroidism in Early Pregnancy. J Womens Health (Larchmt) 2017;26:1231-5. [Crossref] [PubMed]
- Nazarpour S, Tehrani FR, Simbar M, et al. Comparison of universal screening with targeted high-risk case finding for diagnosis of thyroid disorders. Eur J Endocrinol 2016;174:77-83. [Crossref] [PubMed]
- Vaidya B, Anthony S, Bilous M, et al. Detection of thyroid dysfunction in early pregnancy: Universal screening or targeted high-risk case finding? J Clin Endocrinol Metab 2007;92:203-7. [Crossref] [PubMed]
- Chang DL, Leung AM, Braverman LE, et al. Thyroid testing during pregnancy at an academic Boston Area Medical Center. J Clin Endocrinol Metab 2011;96:E1452-6. [Crossref] [PubMed]
- Taylor PN, Minassian C, Rehman A, et al. TSH levels and risk of miscarriage in women on long-term levothyroxine: a community-based study. J Clin Endocrinol Metab 2014;99:3895-902. [Crossref] [PubMed]
- Dosiou C, Barnes J, Schwartz A, et al. Cost-effectiveness of universal and risk-based screening for autoimmune thyroid disease in pregnant women. J Clin Endocrinol Metab 2012;97:1536-46. [Crossref] [PubMed]
- Dosiou C, Sanders GD, Araki SS, et al. Screening pregnant women for autoimmune thyroid disease: a cost-effectiveness analysis. Eur J Endocrinol 2008;158:841-51. [Crossref] [PubMed]
- Chen S, Zhou X, Zhu H, et al. Preconception TSH and pregnancy outcomes: a population-based cohort study in 184 611 women. Clin Endocrinol (Oxf) 2017;86:816-24. [Crossref] [PubMed]
- Abalovich M, Gutierrez S, Alcaraz G, et al. Overt and subclinical hypothyroidism complicating pregnancy. Thyroid 2002;12:63-8. [Crossref] [PubMed]
- Haddow JE, Palomaki GE, Allan WC, et al. Maternal thyroid deficiency during pregnancy and subsequent neuropsychological development of the child. N Engl J Med 1999;341:549-55. [Crossref] [PubMed]
- Laurberg P, Bournaud C, Karmisholt J, et al. Management of Graves' hyperthyroidism in pregnancy: focus on both maternal and foetal thyroid function, and caution against surgical thyroidectomy in pregnancy. Eur J Endocrinol 2009;160:1-8. [Crossref] [PubMed]
- Halperin Y, Caspi E, Leiba IH. Disseminated intravascular coagulation following delivery. Harefuah 1975;89:206-9. [PubMed]
- Stagnaro-Green A. Overt hyperthyroidism and hypothyroidism during pregnancy. Clin Obstet Gynecol 2011;54:478-87. [Crossref] [PubMed]
- van Mil NH, Steegers-Theunissen RP, Bongers-Schokking JJ, et al. Maternal hypothyroxinemia during pregnancy and growth of the fetal and infant head. Reprod Sci 2012;19:1315-22. [Crossref] [PubMed]
- Glinoer D, Riahi M, Grün JP, et al. Risk of subclinical hypothyroidism in pregnant women with asymptomatic autoimmune thyroid disorders. J Clin Endocrinol Metab 1994;79:197-204. [PubMed]
- Casey BM, Dashe JS, Wells CE, et al. Subclinical hypothyroidism and pregnancy outcomes. Obstet Gynecol 2005;105:239-45. [Crossref] [PubMed]
- Cleary-Goldman J, Malone FD, Lambert-Messerlian G, et al. Maternal thyroid hypofunction and pregnancy outcome. Obstet Gynecol 2008;112:85. [Crossref] [PubMed]
- Amouzegar A, Gharibzadeh S, Kazemian E, et al. The Prevalence, Incidence and Natural Course of Positive Antithyroperoxidase Antibodies in a Population-Based Study: Tehran Thyroid Study. PLoS One 2017;12. [Crossref] [PubMed]
- McElduff A, Morris J. Thyroid function tests and thyroid autoantibodies in an unselected population of women undergoing first trimester screening for aneuploidy. Aust N Z J Obstet Gynaecol 2008;48:478-80. [Crossref] [PubMed]
- Negro R, Schwartz A, Gismondi R, et al. Increased pregnancy loss rate in thyroid antibody negative women with TSH levels between 2.5 and 5.0 in the first trimester of pregnancy. J Clin Endocrinol Metab 2010;95:E44-8. [Crossref] [PubMed]
- Toulis KA, Goulis DG, Venetis CA, et al. Risk of spontaneous miscarriage in euthyroid women with thyroid autoimmunity undergoing IVF: a meta-analysis. Eur J Endocrinol 2010;162:643-52. [Crossref] [PubMed]
- Negro R. Thyroid autoimmunity and pre-term delivery: brief review and meta-analysis. J Endocrinol Invest 2011;34:155-8. [Crossref] [PubMed]
- Negro R, Schwartz A, Gismondi R, et al. Thyroid antibody positivity in the first trimester of pregnancy is associated with negative pregnancy outcomes. J Clin Endocrinol Metab 2011;96:E920-4. [Crossref] [PubMed]
- Negro R, Schwartz A, Stagnaro-Green A. Impact of Levothyroxine in Miscarriage and Preterm Delivery Rates in First Trimester Thyroid Antibody-Positive Women With TSH Less Than 2.5 mIU/L. J Clin Endocrinol Metab 2016;101:3685-90. [Crossref] [PubMed]
- Negro R, Formoso G, Mangieri T, et al. Levothyroxine treatment in euthyroid pregnant women with autoimmune thyroid disease: effects on obstetrical complications. J Clin Endocrinol Metab 2006;91:2587-91. [Crossref] [PubMed]
- Nazarpour S, Ramezani Tehrani F, Simbar M, et al. Effects of levothyroxine treatment on pregnancy outcomes in pregnant women with autoimmune thyroid disease. Eur J Endocrinol 2017;176:253-65. [Crossref] [PubMed]
- Negro R, Schwartz A, Gismondi R, et al. Universal screening versus case finding for detection and treatment of thyroid hormonal dysfunction during pregnancy. J Clin Endocrinol Metab 2010;95:1699-707. [Crossref] [PubMed]
- Nazarpour S, Ramezani Tehrani F, Simbar M, et al. Effects of levothyroxine on pregnant women with subclinical hypothyroidism, negative for thyroid peroxidase antibodies. J Clin Endocrinol Metab 2018;103:926-35. [Crossref] [PubMed]
- Smit BJ, Kok JH, Vulsma T, et al. Neurologic development of the newborn and young child in relation to maternal thyroid function. Acta Paediatrica 2000;89:291-5. [Crossref] [PubMed]
- Li Y, Shan Z, Teng W, et al. Abnormalities of maternal thyroid function during pregnancy affect neuropsychological development of their children at 25–30 months. Clin Endocrinol (Oxf) 2010;72:825-9. [Crossref] [PubMed]
- Korevaar TI, Muetzel R, Medici M, et al. Association of maternal thyroid function during early pregnancy with offspring IQ and brain morphology in childhood: a population-based prospective cohort study. Lancet Diabetes Endocrinol 2016;4:35-43. [Crossref] [PubMed]
- Stagnaro-Green A. Second trimester levothyroxine treatment for subclinical hypothyroidism or hypothyroxinaemia of pregnancy does not improve cognitive outcomes of children. Evid Based Med 2017;22:149. [Crossref] [PubMed]
- Lazarus JH, Bestwick JP, Channon S, et al. Antenatal thyroid screening and childhood cognitive function. N Engl J Med 2012;366:493-501. [Crossref] [PubMed]
- Hales C, Channon S, Taylor PN, et al. The second wave of the Controlled Antenatal Thyroid Screening (CATS II) study: the cognitive assessment protocol. BMC endocrine disorders 2014;14:95. [Crossref] [PubMed]
- Hales C, Taylor PN, Channon S, et al. Controlled Antenatal Thyroid Screening II: effect of treating maternal sub-optimal thyroid function on child cognition. J Clin Endocrinol Metab 2018;103:1583-91. [Crossref] [PubMed]
- Casey BM, Thom EA, Peaceman AM, et al. Treatment of Subclinical Hypothyroidism or Hypothyroxinemia in Pregnancy. N Engl J Med 2017;376:815-25. [Crossref] [PubMed]
- Thorpe-Beeston JG, Nicolaides KH, Felton CV, et al. Maturation of the secretion of thyroid hormone and thyroid-stimulating hormone in the fetus. N Engl J Med 1991;324:532-6. [Crossref] [PubMed]
- Thung SF, Funai EF, Grobman WA. The cost-effectiveness of universal screening in pregnancy for subclinical hypothyroidism. Am J Obstet Gynecol 2009;200:267.e1-7. [Crossref] [PubMed]
- De Groot L, Abalovich M, Alexander EK, et al. Management of thyroid dysfunction during pregnancy and postpartum: an Endocrine Society clinical practice guideline. J Clin Endocrinol Metab 2012;97:2543-65. [Crossref] [PubMed]
- Plowden TC, Schisterman EF, Sjaarda LA, et al. Thyroid-stimulating hormone, anti-thyroid antibodies, and pregnancy outcomes. Am J Obstet Gynecol 2017;217:697.e1-7. [Crossref] [PubMed]
Cite this article as: Amouzegar A, Abdi H, Takyar M. Screening for thyroid dysfunction in pregnancy. Ann Thyroid 2018;3:19.