Post-natal Changes in the Intra-abdominal Umbilical Vein

Abstract

Dimensional and histological studies of the intra-abdominal portion of the umbilical vein reveal that soon after birth the vein contracts to one-half its original diameter, the average diameter then being 1.1 mm. Anatomical obliteration begins at or before birth and is well marked by the 28th day. It occurs by a combination of sub-intimal proliferation, the formation and shrinkage of collagen fibers in the fibro-muscular media and side to side flattening. Thrombosis and clot organization are not involved.