Is there an association between subclinical hypothyroidism and preterm uterine contractions? A prospective observational study

* Presentation: Some of the data in this manuscript was presented as a poster presentation at the 34^th SMFM Annual Meeting (“The Pregnancy Meeting”) in New-Orleans, Louisiana on February 2014.

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Abstract

Objective: To investigate the association between subclinical hypothyroidism and preterm contractions.

Methods: Prospective observational study among women at 23 + 0/7 and 34 + 6/7 weeks of gestation, with no known thyroid function abnormality, and preterm uterine contractions (PTC). All patients underwent laboratory evaluation of Thyroid Stimulating Hormone (TSH) and Free Thyroxin (FT4). Patients with and without PTC were compared.

Results: No association was found between PTC and subclinical hypothyroidism. Rate of spontaneous preterm delivery (PTD) was comparable between women with abnormal and normal thyroid function tests. Excluding indicated PTD, patients in the study group had a higher rate of spontaneous PTD (24.7% versus 9.6%, p = 0.03). Patients with past PTD and preterm contractions had higher rates of hypothyroxinemia compared with patients without past PTD (54.6% versus 19.0% and 31.2%, p = 0.001), and patients with past PTD (regardless of the presence or absence of PTC) had higher rate of subclinical hypothyroidism compared with patients with PTC and without PTD (59.1% and 66.7% versus 31.6%, p = 0.017).

Conclusions: No association was found between PTC and subclinical hypothyroidism in the entire cohort, except for patients with preterm contractions and a history of past PTD. This specific group of patients might benefit from thyroid function evaluation.

Keywords:

• Hypothyroidism
• hypothyroxinemia
• preterm labor
• preterm uterine contractions

Acknowledgements

The authors wish to thank and acknowledge Mrs. Rachel Adani from the endocrine laboratory at the Rabin Medical Center for her much appreciated assistance.

Ethics approval: This study was approved by the local institutional review board (“The Helsinki Committee. Approval number 0462-12-RMC, January 2013) and all patients provided written informed consent for their participation.

Declaration of interest

All authors report no conflicts of interests. No funding was granted for the performance of this trial.

Notes

* Presentation: Some of the data in this manuscript was presented as a poster presentation at the 34^th SMFM Annual Meeting (“The Pregnancy Meeting”) in New-Orleans, Louisiana on February 2014.