Pathophysiology
The umbilical cord connects the fetus to the mother in utero. Composed of connective tissue and blood vessels, the cord is cut immediately after birth, leaving the umbilical stump. Normally, the cord area is colonized with potential bacterial pathogens during or soon after birth. These bacteria attract polymorphonuclear leukocytes to the umbilical cord. Although the precise mechanisms of umbilical cord separation are unknown, granulocyte influx and phagocytosis, as well as desiccation, tissue infarction and necrosis, and the activity of collagenase and other proteases, all contribute to the process.
The umbilical stump represents a unique, but universally acquired, wound that, as the tissue undergoes devitalization, provides a medium that supports the growth of bacteria. These bacteria have the potential to invade the umbilical stump, leading to omphalitis. If this occurs, the infection may progress beyond the subcutaneous tissues to involve fascial planes (necrotizing fasciitis), abdominal wall musculature(myonecrosis), and, when the bacteria invade the umbilical vessels, the umbilical and portal veins (phlebitis). The factors that cause colonization to progress to infection are not well understood. The image below shows the anatomic relationship between the umbilicus and its embryologic attachments