Association of Maternal Thyroglobulin Antibody with Preterm Birth in Euthyroid Women.

Background: While the association between maternal thyroid peroxidase antibody (TPOAb) positivity and preterm birth (PTB) risk has been established, the association between thyroglobulin antibody (TgAb) and PTB remains unclear.

Objective: This study aimed to explore the association between TgAb and PTB risk in euthyroid women.

Methods: This single-center, prospective cohort study enrolled euthyroid women in the first trimester. Data on serum concentrations of thyroid-stimulating hormone (TSH), free thyroxine (FT4), TgAb, and TPOAb was collected. Participants were categorized into two groups (TgAb-negative and TgAb-positive). PTB was subtyped into spontaneous PTB (S-PTB) and medically-induced PTB (MI-PTB); and into early PTB (E-PTB) and late PTB (L-PTB). Logistic regression models examined the associations between TgAb and PTB and its subtypes, with stratification by first-trimester TSH levels (0.1-2.5 mIU/L, 2.5-4.0 mIU/L).

Results: This study comprised of 58,247 euthyroid pregnant women. Adjusting for confounders, TgAb positivity was associated with a 16% increased risk of PTB (adjusted odds ratio (aOR) 1.16, 95% confidence interval (CI) 1.03-1.29, P=0.01) compared to the TgAb-negative group. Specifically, TgAb positivity showed higher risk of S-PTB and L-PTB, aOR 1.22 (95% CI 1.06, 1.39) and aOR 1.17 (95%CI 1.04, 1.32), respectively. Consistent results were observed when analyzing TgAb concentration as a continuous variable. TSH stratification analysis revealed that these associations were significant only among women with TSH levels between 0.1-2.5 mIU/L.

Conclusions: In euthyroid women, TgAb positivity was associated with higher risk of PTB that mainly manifested as S-PTB and L-PTB. However, the clinical significance of these findings is limited.