Umbilical Artery Thrombosis in Pregnancy: A Systematic Review and Case-based Insight into Doppler Diagnosis, Pathophysiology, and Perinatal Outcomes

Background: Umbilical artery thrombosis (UAT) is a rare but important cause of fetal compromise. Once considered a postnatal diagnosis, improved Doppler ultrasonography now permits antenatal identification. A unified synthesis of diagnostic features, mechanisms, and outcomes is needed to support clinical decision-making. The objective of the study is to summarize prenatal diagnostic characteristics, underlying pathophysiology, and perinatal outcomes of UAT, complemented by an illustrative clinical case. Methods: A PRISMA-guided search of PubMed, Scopus, Embase, and Web of Science through September 2025 identified reports describing prenatal or perinatal UAT confirmed by Doppler ultrasonography or histopathology. Fifty-five studies met the inclusion criteria. Extracted data included gestational age at diagnosis, Doppler findings, associated factors, mechanistic context, and outcomes. Study quality was appraised using NOS, JBI, AMSTAR-2, and ROBIS. Results: Diagnosis occurred between 10 and 39 weeks, most often in the late second or third trimester. The hallmark prenatal finding was unilateral absent end-diastolic velocity with preserved flow in the contralateral artery. Additional indicators included color asymmetry, flow-trajectory disturbance, and wave-reflection changes. Mechanistic patterns reflected Virchow's triad, encompassing stasis, hypercoagulability, endothelial injury, and structural or placental contributors. Perinatal outcomes were generally favorable when unilateral thrombosis was detected and monitored, whereas unrecognized or bilateral occlusion was associated with fetal growth restriction or intrauterine demise. An illustrative case confirmed the value of advanced Doppler trajectory mapping in enabling early diagnosis and timely delivery. Conclusion: Targeted Doppler interrogation allows reliable prenatal detection of UAT. Incorporating mechanistic Doppler markers and standardized reporting may enhance diagnostic accuracy and support informed delivery planning.