The umbilical cord usually grows from the centre of the placenta, but it may grow from the edge of the placenta or occasionally from the membranes or sac. The other end of the cord attaches to the baby's navel or umbilicus.
The cord grows to be approximately 1 to 2 cm thick and up to 50cm in length or so. It contains two arteries and one vein entwined and enclosed by a protective, gristly substance called Wharton's Jelly, which makes the cord slippery, allowing it to move freely around your baby. Blood constantly pulsates through the cord with every beat of your baby's heart. The cord contains no nerves (similar to your hair or fingernails) so when it is cut at birth there is no pain experienced by mother or baby.
Updated November 2007
Information sources
Stables D. and Rankin J. Physiology in Childbearing with Anatomy and Related Biosciences. 2004, Bailliere Tindall, Edinburgh.