Log-Transformed TSH–Thyroglobulin Product as a Predictor of Placenta Previa and Placental Abruption

<b>Introduction: </b>Thyroid hormones are essential for placental development, and subtle disruptions may contribute to placenta previa (PP) and placental abruption (PA). This study evaluated thyroid hormone levels and derived log ratios to identify associations with delivery outcomes and predictors of PP/PA.<br /> <b>Methods: </b>In this prospective study, 347 singleton pregnancies at a tertiary obstetric center were included, excluding women with thyroid or chronic disease, smoking, thyroid-affecting medications, or fetal anomalies. Maternal demographic and obstetric data were collected from medical records. Dried blood spot samples were analyzed for thyroid-stimulating hormone (TSH), total thyroxine (TT4), and thyroglobulin (Tg), and urinary iodine concentration (UIC) was measured. Derived thyroid hormone log ratios—including TSH/TT4, TT4/Tg, TSH∙Tg, UIC/TT4 were calculated.<br /> <b>Results: </b>Correlations with PP/PA were: TSH (0.50 mU/L; r = –0.123, p = 0.022), Tg (9.42 µg/L; r = –0.119, p = 0.027), log(TSH/TT4) (–2.359 ± 0.283; r = –0.168, p = 0.002), log(TT4/Tg) (1.063±0.366; r = 0.187, p = 0.0005), log(TSH·Tg) (0.574±0.511; r = –0.216, p < 0.001). Logistic regression: log(TSH·Tg) [OR (odds ratio) = 0.16, p = 0.016; log(UIC/TT4) OR = 0.01, p = 0.055. Receiver operating characteristic analysis showed area under the curve 0.857, sensitivity/specificity pair = 100%/61.2% at cutoff < 0.4958, criterion = 0.4958.<br /> <b>Conclusions: </b>Log(TSH·Tg) is a strong independent predictor of PP/PA with high sensitivity and moderate specificity. It outperforms individual thyroid measures and may support early risk stratification by reflecting subtle maternal thyroid dysregulation affecting placental development.