American Thyroid Association
American Thyroid Association
October 31, 2019
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High, low preconception TSH levels may predict preterm delivery

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CHICAGO— Using multiples of median calculations to assess thyroid-stimulating hormone levels among more than 4.3 million women in rural China, researchers found that risks for delivering a baby before term were elevated for both those with low and those with high TSH values, according to data presented at the American Thyroid Association annual meeting.

Ying Yang

“Multiples of the median (MoM) is usually used for screening test results, especially when the results of each test show considerable differences or variations. This method is universally used in prenatal screening of Down syndrome and neural tube defects,” Ying Yang, PhD, associate professor of epidemiology at National Research Institute for Health and Family Planning and the National Human Genetic Resources Center in Beijing, told Endocrine Today. “Although a preconception care strategy has been proved beneficial for maternal and child health, which is explicitly mentioned in 2017 Guidelines of the American Thyroid Association for the Diagnosis and Management of Thyroid Disease During Pregnancy and the Postpartum, there is still insufficient evidence to support such a screening approach, with the exception of women planning assisted reproduction or those known to have positive thyroid peroxidase antibodies. Our study provides evidence support for preconception screening of reproductive-aged women for thyroid function to some extent.”

Yang and colleagues analyzed data from the National Free Pre-pregnancy Checkups Project in China collected between 2013 and 2016 on preconception TSH levels, family history and pregnancy history for 4,324,810 reproductive-aged women, with follow-up through 2017.

Prevalence of preterm delivery was 6.64% among the cohort. Compared with women with TSH levels between 0.4 mIU/L and 2.49 mIU/L as the reference group — who had a preterm delivery rate of 6.51% — women with TSH levels lower than 0.1 mIU/L had the highest preterm delivery rate at 7.98% for an adjusted OR of 1.24 (95% CI, 1.17-1.3). Women with TSH levels between 4.97 mIU/L and 9.99 mIU/L and greater than 10 mIU/L had aORs of 1.18 (95% CI, 1.14-1.22) and 1.11 (95% CI, 1.03-1.21), respectively.

Using multiples of median calculations to assess thyroid-stimulating hormone levels among more than 4.3 million women in rural China, researchers found that risks for delivering a baby before term were elevated for both those with low and those with high TSH values.
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Odds of preterm delivery were at least 20% higher among women with TSH MoM values lower than 0.4 or higher than 4.5 compared with values between 0.9 and 1.49, according to Yang.

“The large sample size of our study enables us to divide maternal preconception TSH into different levels and provide enough power for detection of the associations. Furthermore, preconception TSH were converted to TSH MoM values to overcome the variability or systematic differences between various laboratories or assays,” Yang said. “U-shaped relationships between preconception TSH level/MoMs and preterm birth risk were identified. Decreasing or increasing preconception TSH levels can significantly increase the risk of preterm birth.” – by Jill Rollet

Reference:

Yang Y. Oral abstract 15. Presented at: 89th Annual Meeting of the American Thyroid Association; Oct. 30-Nov. 3, 2019; Chicago.

Disclosure: Yang reports no relevant financial disclosures.