Are Thyroid Test Abnormalities a Risk Factor for Preterm Birth?
BACKGROUND AND PURPOSE:
Korevaar et al. (JAMA, 2019) investigated whether maternal thyroid function test levels associated with non-overt, milder thyroid abnormalities and thyroid autoimmunity are risk factors for preterm birth
Systematic review and meta-analysis
Study conducted by the Consortium on Thyroid and Pregnancy—Study Group on Preterm Birth (collaboration of prospective birth cohorts)
Individual data was collected so that definitions for thyroid test levels could be standardized
Published data: Ovid MEDLINE, EMBASE, Web of Science, the Cochrane Central Register of Controlled Trials, and Google Scholar databases
Unpublished data: Open invitations sent to relevant journals, international conferences, social media, and personal contacts
Published and unpublished prospective cohort studies
Studies with data on relevant thyroid function tests
Exclusion: Studies only including overt thyroid disease or treatment was administered based on abnormal thyroid function tests
Subclinical hypothyroidism: Increased thyrotropin concentration with normal FT4 concentration
Isolated hypothyroxinemia: Decreased FT4 concentration with normal thyrotropin concentration
Data synthesis and analysis
Studies screened by 2 independent reviewers
Individual participant data were analyzed using mixed-effects models
Adjustments made for: Maternal age | BMI | Ethnicity | Smoking | Parity | Gestational age at blood sampling | Fetal sex
Primary outcome: Preterm birth (<37 weeks)
Secondary outcome: Very preterm birth (<32 weeks)
19 cohorts were included | 47,045 pregnant women | 5.0% preterm birth
Subclinical hypothyroidism: 3.1%
Isolated hypothyroxinemia: 2.2%
TPO antibody positive: 7.5%
Risk of preterm birth was higher for subclinical hypothyroidism (6.1%) vs euthyroid (5.0%)
Odds ratio (OR) 1.29 (95% CI, 1.01 to 1.64)
Risk of preterm birth was higher for isolated hypothyroxinemia (7.1%) vs euthyroid (5.0%)
OR 1.46 (95% CI, 1.12 to 1.90)
Risk also increased for very preterm birth (OR 2.57; 95% CI, 1.55 to 4.27)
Each 1-SD higher maternal TSH concentration was associated with a higher risk of preterm birth
Absolute risk difference 0.2% (95% CI, 0% to 0.4%) per 1 SD
OR 1.04 (95% CI, 1.00 to 1.09) per 1 SD
TPO antibody–positive had a higher risk of preterm birth vs TPO antibody–negative
Absolute risk difference 1.6% (95% CI, 0.7% to 2.8%)
OR 1.33 (95% CI, 1.15 to 1.56)
Risk was also increased for very preterm birth (OR 2.45; 95% CI, 1.81 to 3.32)
Subclinical hypothyroidism, isolated
hypothyroxinemia, and TPO antibody positivity were associated with a higher
risk of preterm birth
Authors suggest that while these results do not
support universal thyroid screening in pregnancy
The results support the concept of a reflex TPO antibody measurement in women with a thyrotropin concentration higher than 4.0 mIU/L, and gestational thyrotropin monitoring for TPO antibody–positive women prior to conception.
An accompanying editorial (see ‘Learn More – Primary Sources’) points out that routine screening for TSH, free thyroxine and TPO antibody is not recommended by ACOG or the American Thyroid Association based on previous RCTs and further states
Several recent large, well-done clinical trials that assessed the effect of routine pregnancy screening for and thyroid hormone treatment of subclinical hypothyroidism, isolated hypothyroxinemia, and TPO antibody positivity have failed to show benefit. It seems plausible that these thyroid testing abnormalities may reflect other nonthyroidal processes rather than thyroid dysfunction.
OBG Project CME requires a modern web browser (Internet Explorer 10+, Mozilla Firefox, Apple Safari, Google Chrome, Microsoft Edge). Certain educational activities may require additional software to view multimedia, presentation, or printable versions of their content. These activities will be marked as such and will provide links to the required software. That software may be: Adobe Flash, Apple QuickTime, Adobe Acrobat, Microsoft PowerPoint, Windows Media Player, or Real Networks Real One Player.
Disclosure of Unlabeled Use
This educational activity may contain discussion of published and/or investigational uses of agents that are not indicated by the FDA. The planners of this activity do not recommend the use of any agent outside of the labeled indications.
The opinions expressed in the educational activity are those of the faculty and do not necessarily represent the views of the planners. Please refer to the official prescribing information for each product for discussion of approved indications, contraindications, and warnings.
Participants have an implied responsibility to use the newly acquired information to enhance patient outcomes and their own professional development. The information
presented in this activity is not meant to serve as a guideline for patient management. Any procedures, medications, or other courses of diagnosis or treatment discussed or suggested in this activity should not be used by clinicians without evaluation of their patient’s conditions and possible contraindications and/or dangers in use, review of any applicable manufacturer’s product information, and comparison with recommendations of other authorities.
Jointly provided by
NOT ENOUGH CME HOURS
It appears you don't have enough CME Hours to take this Post-Test. Feel free to buy additional CME hours or upgrade your current CME subscription plan