Evaluation of functional spiral artery count and jet dispersion index using power Doppler ultrasound: in vivo insights into the vascular pathology of placental dysfunction.

OBJECTIVE: To evaluate two novel vascular markers - functional spiral artery (FSA) count and jet dispersion index (DI)-derived from first-trimester 3D placental power Doppler ultrasound, and to assess their association with pre-eclampsia (PE) and fetal growth restriction (FGR). METHODS: We analysed a combined dataset of 6246 pregnancies from two prospective cohort studies (FirstPLUS and OxPLUS). Participants underwent 3D placental ultrasound between 11 + 2 and 14 + 1 weeks' gestation. Images were processed using the OxNNet convolutional neural network for automated segmentation of placental and vascular structures. FSAs were defined as vessel segments crossing the uteroplacental interface and terminating within placental tissue. DI quantified vessel dispersion relative to length. Associations between vascular markers and pregnancy outcomes were assessed using logistic regression. RESULTS: Of 6246 cases, 5555 yielded evaluable FSA counts and 2991 yielded DI results. Lower FSA count z-score was associated with FGR (median z-score -0.05 vs 0.08, P < 0.001), but not significantly with PE. Lower mean DI was associated with both PE (median z-score -0.22 vs 0.05, P = 0.005) and FGR (median z-score -0.31 vs 0.06, P < 0.001). Odds of adverse outcomes decreased with higher FSA count and FSA mean DI values. CONCLUSION: Reduced terminal vessel number and dispersion in early pregnancy are associated with placental insufficiency syndromes. These novel ultrasound-derived markers may provide predictive insights into the haemodynamic basis of PE and FGR.