MR Imaging of Umbilical Cord Variations, Abnormalities, and Associated Placental Findings.

The umbilical cord and placenta, classified as fetal appendages, play a crucial role in fetal growth and survival. While ultrasonography remains the primary modality for evaluation, MRI provides a more objective and comprehensive assessment, particularly for the placenta and fetus. Although MRI assessment of the umbilical cord is still emerging and not yet widely adopted by radiologists, MRI has the potential to support and complement ultrasound findings, thereby contributing to safer perinatal management. This review summarizes key MRI findings related to the umbilical cord and associated placental abnormalities. In cases where MRI reports are currently unavailable, ultrasound findings are included to supplement the discussion and to support inferences of potential MRI findings, encouraging future diagnostic applications. Initially, we describe the normal morphology and physiological changes of the umbilical cord and placenta, recommended MRI sequences, and normal imaging findings. Placental abnormalities associated with umbilical cord anomalies, including morphological and positional abnormalities, are reviewed. Variations in umbilical cord insertion, particularly marginal and velamentous insertion, as well as vasa previa, are also discussed. Abnormalities related to umbilical cord position and morphology, such as hypercoiling and hypocoiling, cord knots, nuchal cords, and cord presentation, are examined. Additionally, vascular abnormalities, including single umbilical artery, fused umbilical artery, supernumerary vessels, varices, and aneurysms, are explored along with their underlying mechanisms. Finally, umbilical cord cysts and umbilical cord ulcers are addressed. Advancements in imaging technology, particularly Doppler ultrasonography, have significantly improved the detection and management of umbilical cord and placental abnormalities. Understanding these abnormalities in prenatal MRI evaluation is crucial for improving diagnostic accuracy and optimizing perinatal care. MRI may prove to be a useful adjunct when ultrasound findings are inconclusive or when additional anatomical and functional information is needed. However, further studies are needed to clarify MRI's clinical utility.