Septic thrombophlebitis of the umbilical vein (SVT) is a serious pathology in neonates, characterized by inflammation of the umbilical vein due to bacterial infection, with 90% of cases linked to the use of central venous catheters (CVCs). This inflammation can lead to thrombus formation as part of the immune system's response. Premature newborn, 33 weeks gestation, delivered vaginally, with history of gestational diabetes, twin pregnancy, macrosomia and premature rupture of membranes (57 hours), initially well adapted to extrauterine life, with a birth weight of 1575 g. The infant was admitted to neonatology for respiratory distress, and an intrahepatic umbilical catheter was inserted. On the 5th day of hospitalization, the infant developed a nosocomial Klebsiella pneumoniae infection, complicated by a fulminant hemorrhagic syndrome with hematemesis and melena. The clinical course was further complicated by multivisceral failure, requiring hepatic Doppler ultrasound, which revealed umbilical vein thrombosis. The newborn was treated with curative doses of Lovenox, while targeted antibiotic therapy was maintained for three weeks after negative blood cultures, resulting in significant clinical and biological improvement. Based on this case, we conclude that it is advisable to think about umbilical vein thrombosis and to perform an abdominal ultrasound in the presence of any digestive hemorrhage in a newborn or an intrahepatic or peripheral umbilical venous catheter, or in subjects at risk (hypotrophy, polycythemia, transfusion on the catheter) in order to screen for possible umbilical or portal vein thrombosis.