Objective: To evaluate the predictive value of serum vitamin D (VD), D-dimer, combined with uterine artery blood flow parameters and multimodal ultrasound score for pregnancy loss in patients with unexplained recurrent spontaneous abortion (URSA), from the perspective of imaging-based risk stratification. Methods: A retrospective analysis was conducted on 200 URSA patients. Based on pregnancy outcomes, they were divided into a normal pregnancy group (n=100) and a pregnancy loss group (n=100). Clinical characteristics, serological markers (VD, D-dimer), and ultrasound parameters, including the multimodal ultrasound score, uterine artery systolic/diastolic velocity ratio (S/D), resistance index (RI), and pulsatility index (PI), were compared between the two groups. Binary Logistic regression analysis was used to identify imaging and serological factors associated with pregnancy loss in URSA patients. The predictive performance of individual and combined indicators was evaluated using receiver operating characteristic (ROC) curve analysis. Results: Compared with the normal pregnancy group, the pregnancy loss group had a higher number of previous miscarriages (P<0.001), lower serum VD levels and higher D-dimer levels (P<0.001). The multimodal ultrasound score was lower (P <0.001), while uterine artery S/D and RI were higher (P<0.05). Binary Logistic regression analysis revealed that decreased serum VD level (OR =0.955, 95% CI:0.931~0.980), increased D-dimer level (OR=5.585, 95% CI:2.066~15.098), decreased multimodal ultrasound score (OR=0.585, 95%CI:0.470~0.728), and increased uterine artery S/D ratio (OR=1.383, 95%CI:1.139~1.680) were independently associated with pregnancy loss in URSA patients. ROC curve analysis showed that the area under the curve (AUC) for the combined application of these indicators was 0.925 (95% CI:0.880~0.958), which was higher than that of any single indicator (P<0.001). Conclusion: Decreased serum VD, increased D-dimer, a lower multimodal ultrasound score, and an elevated uterine artery S/D ratio reflect high-risk imaging features associated with pregnancy loss in URSA patients. A comprehensive assessment centered on multimodal ultrasound, combined with serological markers, facilitates imaging-based risk stratification for pregnancy in URSA patients and provides a reference for pregnancy outcome evaluation.