Association of Thyroid Function Test Abnormalities and Thyroid Autoimmunity With Preterm Birth: A Systematic Review...

Area of Science:

• Reproductive endocrinology and maternal-fetal medicine.
• Thyroid disease in pregnancy and its impact on obstetric outcomes.

Background:

• Maternal hypothyroidism and hyperthyroidism are established risk factors for preterm birth.
• The association between milder thyroid function abnormalities, thyroid autoimmunity, and preterm birth remains controversial.
• Understanding these associations is crucial for optimizing prenatal care and screening protocols.

Purpose of the Study:

• To investigate whether maternal thyroid function test abnormalities and thyroid autoimmunity are risk factors for preterm birth.
• To analyze the association between subclinical hypothyroidism, isolated hypothyroxinemia, and thyroid peroxidase (TPO) antibody positivity with preterm birth risk.

Main Methods:

• A systematic review and meta-analysis of prospective cohort studies was conducted.
• Data from 19 cohorts, including 47,045 pregnant women, were analyzed.
• Thyroid function tests (thyrotropin [TSH] and free thyroxine [FT4]) and TPO antibody measurements were assessed against preterm birth outcomes.

Main Results:

• Subclinical hypothyroidism (OR, 1.29) and isolated hypothyroxinemia (OR, 1.46) were significantly associated with an increased risk of preterm birth.
• Maternal TPO antibody positivity also correlated with a higher risk of preterm birth (OR, 1.33).
• Increased thyrotropin concentration was continuously associated with a higher risk of preterm birth.

Conclusions:

• Subclinical hypothyroidism, isolated hypothyroxinemia, and TPO antibody positivity are significant risk factors for preterm birth in pregnant women without overt thyroid disease.
• These findings support the consideration of screening for these conditions during pregnancy.
• The results inform clinical decision-making regarding the potential benefits and harms of screening and levothyroxine treatment.