Practice Variation in the Care of Subclinical Hypothyroidism During Pregnancy

A National Survey of Physicians in the United States

Freddy J.K. Toloza; Naykky M. Singh Ospina; Rene Rodriguez-Gutierrez; Derek T. O'Keeffe; Juan P. Brito; Victor M. Montori; Spyridoula Maraka


J Endo Soc. 2019;3(10):1892-1906. 

In This Article

Abstract and Introduction


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.


Subclinical hypothyroidism (SCH) in pregnancy is a mild thyroid disorder defined by an elevated serum TSH level with a normal free thyroxine (FT4) level.[1] As a result of physiological changes in thyroid function during pregnancy leading to increased maternal thyroid hormone demand, SCH is a common condition among pregnant women.[2–4] During pregnancy, overt hypothyroidism, defined as an elevated TSH level with a low FT4 level, contributes to adverse maternofetal and offspring outcomes.[5–9] Accordingly, treatment with levothyroxine (LT4) is strongly recommended.[1,10] For pregnant women with SCH, however, the evidence for both adverse outcomes and the ability of LT4 treatment to prevent them is unclear,[11–15] and the clinical recommendations are inconsistent.[1,10,16]

In 2012, the Endocrine Society published a clinical practice guideline for the management of thyroid diseases in pregnancy and recommended that all pregnant women with SCH be treated with LT4, independent of thyroid peroxidase antibody (TPO-Ab) status.[10] In the 2015 clinical management guidelines of the American College of Obstetricians and Gynecologists (ACOG), universal screening for thyroid disease in pregnancy was not recommended on the basis of evidence that identification and treatment of maternal SCH has not improved neurocognitive function in offspring.[16] In 2017, the American Thyroid Association (ATA) issued new guidelines that changed the TSH threshold used to define SCH and emphasized the use of TPO-Ab status to determine whether to treat SCH with LT4.[1] Specifically, the TSH upper limit was raised from 2.5 to 4.0 mIU/L when no population-based cutoff is available, and evaluation of TPO-Ab status was recommended in all pregnant women with TSH concentrations >2.5 mIU/L, with the result contributing to the treatment decision.

The inconsistencies noted in the recommendations from different organizations may be due to different publication times, which allowed evaluation of more data in the more recent guidelines. The paucity of reliable evidence and variations in recommendations may contribute to unwarranted practice variations. A recent study using a US national administrative database showed that of 8040 pregnant women with SCH (TSH level of 2.5 to 10 mIU/L), only 15% were started on LT4 treatment. Furthermore, endocrinologists had a lower TSH threshold for starting LT4 treatment compared with internists, obstetricians, and other clinicians.[17] Moreover, previous studies assessing the management of thyroid disorders during pregnancy have shown wide variations in practice among physicians worldwide.[18–22]

To better understand the effect of the most recent ATA guidelines on the care of pregnant women with SCH in the United States, we surveyed physicians nationwide to assess their knowledge and perceptions of the diagnosis, treatment, and effect of SCH in pregnancy and compared these findings with ATA recommendations for care.