NEONATAL VASCULAR THROMBOSIS is rare; however, it is emerging as a more frequent problem in tertiary neonatal care.1Both the incidence and severity of thromboembolic events are increasing in children, with newborns being the largest group affected.2A 1995 Canadian study estimated that the incidence of clinically diagnosed cases of neonatal thrombosis was 2.4 per 1,000 admissions.3A two-year study published in Germany in 1997 reported 5.1 per 100,000 births.4The first study reported that thrombotic disease diagnosed in neonates is most commonly associated with the presence of an indwelling intravascular catheter. The second study reported that most venous thromboses were diagnosed in the second week of life in premature or mature infants in the upper venous system and were directly associated with indwelling central catheters. Although spontaneous thrombosis does occur, it is usually confined to the renal veins.3