The Endocrine Society's 94th Annual Meeting and Expo:

Subclinical Hypothyroidism During Pregnancy Can Increase Serious Complications

During pregnancy, overt hypothyroidism can lead to complications for both mother and baby.  This has been well studied, but the effects of subclinical hypothyroidism on pregnancy have not been studied as much.  What levels of thyroid dysfunction can lead to complications?

At the 94th Annual Meeting of The Endocrine Society, researchers from the Christian Medical College and Hospital (Ludhiana Punjab, India) presented results from a study on subclinical hypothyroidism during pregnancy.  The study was “Increased Pregnancy Losses and Poor Neonatal Outcomes in Women with First Trimester TSH Levels between 2.5 to 4 mlU/L Compared to Euthyroid Women with TSH Levels Less Than or Equal to 2.5.”1

The study was part of the Thyroid Screening in Urban Ludhiana Pregnancy Study (TULIPS), which is a prospective study on thyroid function screening during the first trimester.

The researchers examined the following outcomes:

  • Early and late pregnancy losses
  • 12 maternal complications (including preterm delivery)
  • 5 neonatal complications
  • Birth weight

TSH levels were tested during the first trimester, and 2 groups were formed based on those levels.  Group A (n = 533) had TSH ≤ 2.5 mlU/L; Group B (n = 263) had TSH > 2.5 mlU/L but ≤ 4 mlU/L.  Any woman with TSH > 4 mlU/L was treated with levothyroxine and was not included in this study.

Effects of Subclinical Hypothyroidism in This Study
In Group B, there was a significant increase in early (≤ 20 weeks) and late (> 20 weeks) pregnancy loss when compared to Group A (Early: 8.4% vs 4.1%, p < 0.001 [Odds Ratio (OR) 95% confidence interval (CI) 2.1 (1.1-3.9)] and Late: 4.2% vs 0.6%, p < 0.001 [OR (95% CI) 7.7 (2.1-27.8)]).

For preterm delivery, the odds (95% CI) in Group B were 2.02 (1.1-3.7) when compared to Group A. 

As for the baby’s health, children born to Group B women had significantly higher odds of having a low birth weight (24.2% vs 16.6%, p = 0.01 [OR (95% CI) 1.6 (1.1-2.3)]).

What These Results Mean for Thyroid Function Screening During Pregnancy
Lead author of the study, Jubbin Jagan Jacob, MD, says, “These finding add to the now increasing evidence from previous studies that all pregnant women, irrespective of their risk for thyroid problems, probably should be screened for thyroid dysfunction with the first three months of getting pregnant.”

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