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Observational Study
. 2017 Jan 25:356:i6865.
doi: 10.1136/bmj.i6865.

Thyroid hormone treatment among pregnant women with subclinical hypothyroidism: US national assessment

Spyridoula Maraka  1   2 , Raphael Mwangi  3 , Rozalina G McCoy  4   5 , Xiaoxi Yao  3   6 , Lindsey R Sangaralingham  3   7 , Naykky M Singh Ospina  2   8 , Derek T O'Keeffe  9   10 , Ana E Espinosa De Ycaza  10 , Rene Rodriguez-Gutierrez  2   11 , Charles C Coddington 3rd  12 , Marius N Stan  10 , Juan P Brito  2   10 , Victor M Montori  2   10
Affiliations
Observational Study

Thyroid hormone treatment among pregnant women with subclinical hypothyroidism: US national assessment

Spyridoula Maraka et al. BMJ. .

Abstract

Objective: To estimate the effectiveness and safety of thyroid hormone treatment among pregnant women with subclinical hypothyroidism.

Design: Retrospective cohort study.

Setting: Large US administrative database between 1 January 2010 and 31 December 2014.

Participants: 5405 pregnant women with subclinical hypothyroidism, defined as untreated thyroid stimulating hormone (TSH) concentration 2.5-10 mIU/L.

Exposure: Thyroid hormone therapy.

Main outcome measure: Pregnancy loss and other pre-specified maternal and fetal pregnancy related adverse outcomes.

Results: Among 5405 pregnant women with subclinical hypothyroidism, 843 with a mean pre-treatment TSH concentration of 4.8 (SD 1.7) mIU/L were treated with thyroid hormone and 4562 with a mean baseline TSH concentration of 3.3 (SD 0.9) mIU/L were not treated (P<0.01). Pregnancy loss was significantly less common among treated women (n=89; 10.6%) than among untreated women (n=614; 13.5%) (P<0.01). Compared with the untreated group, treated women had lower adjusted odds of pregnancy loss (odds ratio 0.62, 95% confidence interval 0.48 to 0.82) but higher odds of preterm delivery (1.60, 1.14 to 2.24), gestational diabetes (1.37, 1.05 to 1.79), and pre-eclampsia (1.61, 1.10 to 2.37); other pregnancy related adverse outcomes were similar between the two groups. The adjusted odds of pregnancy loss were lower in treated women than in untreated women if their pre-treatment TSH concentration was 4.1-10 mIU/L (odds ratio 0.45, 0.30 to 0.65) but not if it was 2.5-4.0 mIU/L (0.91, 0.65 to 1.23) (P<0.01).

Conclusion: Thyroid hormone treatment was associated with decreased risk of pregnancy loss among women with subclinical hypothyroidism, especially those with pre-treatment TSH concentrations of 4.1-10 mIU/L. However, the increased risk of other pregnancy related adverse outcomes calls for additional studies evaluating the safety of thyroid hormone treatment in this patient population.

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Conflict of interest statement

All authors have completed the ICMJE uniform disclosure form at www.icmje.org/coi_disclosure.pdf (available on request from the corresponding author) and declare: support from the Agency for Healthcare Research and Quality and AcademyHealth for the submitted work; no financial relationships with any organizations that might have an interest in the submitted work in the previous three years; no other relationships or activities that could appear to have influenced the submitted work.

Figures

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Fig 1 Cohort creation flowchart
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Fig 2 Distribution of thyroid stimulating hormone (TSH) in treated and untreated groups
See this image and copyright information in PMC

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