Abstract
OBJECTIVE: To identify factors associated with indicated preterm birth (IPB) based on early pregnancy placental three-dimensional power Doppler ultrasound (3D-PDU) indices and maternal clinical characteristics, and to develop and validate a predictive model for IPB. METHODS: A total of 458 singleton pregnancies from 2022 were retrospectively analyzed. Early pregnancy placental 3D-PDU indices-vascularization index (VI), flow index (FI), vascularization-flow index (VFI)-along with maternal clinical characteristics, were collected. Subjects were randomly divided into a training set and a test set (7:3 ratio), and further categorized into the IPB group or the full-term group based on pregnancy outcomes. Logistic regression analysis and Akaike Information Criterion (AIC) were used to identify predictors and construct an IPB prediction model. Model performance was evaluated using discrimination, calibration, and clinical utility metrics. RESULTS: Multifactorial logistic regression identified a history of recurrent pregnancy loss, preterm birth history, and hypertensive disorders of pregnancy as independent risk factors for IPB, while early-pregnancy placental VFI was an independent protective factor. Based on the filter results, a nomogram model was plotted, which showed good discrimination (AUC: 0.900 [training set] and 0.882 [test set]). Hosmer-Lemeshow tests indicated good calibration (P = 0.449 for training set, P = 0.585 for test set), and decision curve analysis confirmed clinical utility. CONCLUSION: The 3D-PDU indices, particularly VFI, may serve as valuable indicators of early placental perfusion. The nomogram developed in this study showed good predictive performance by integrating the early pregnancy placental 3D-PDU index (VFI) with maternal clinical characteristics, providing a potential tool for early identification of high-risk IPB pregnancies. Nonetheless, larger multicenter, prospective studies are needed to validate its applicability, and standardized protocols for 3D-PDU use should be established to ensure consistency.