Abstract
INTRODUCTION: To clarify the uncertain association between maternal total triiodothyronine (TT3) levels and preeclampsia risk. METHODS: In a hospital-based cohort of pregnant women with universal thyroid testing, we assessed the association between TT3 and preeclampsia using directed acyclic graphs (DAG) to control confounders. RESULTS: Maternal TT3 levels were associated with preeclampsia risk, with an adjusted odd ratio (OR) of 2.32 (95% confidence interval (CI) 2.02-2.68) in women with the highest TT3 quartile comparing to those in the lowest quartile. A J-shaped association was identified for early onset preeclampsia, with particularly strong association when thyroid-stimulating hormone exceeded 2.5 μIU/mL (OR, 17.22, 95% CI 4.52-65.60). Gestational age > 18 weeks at measurement significantly modified the effect of TT3 on preeclampsia risk, with an interaction OR of 3.22 (95% CI 1.56-6.62). CONCLUSION: Increased maternal TT3 levels were associated with preeclampsia. TT3 may contribute to preeclampsia pathogenesis and serve as a clinical biomarker, especially for early onset cases with thyroid dysfunction.