The umbilical arterial catheterization is warranted by more accurate measurement of arterial blood gas, easier administration of fluid and easier nursing care. However, a variety of complications of umbilical arterial catheterization in the newborn have been reported before. This paper describes a 7 months male infant in whom an umbilical arterial catheter may have been a cause of development of an aortic aneurysm. It is suggested that the mechanical effect of the catheter gave a damage to the aortic wall associated with infection, which is considered as the cause of the aneurysm. The surgical treatment of aortic aneurysm in infancy is discussed.
