Inside the placenta, the umbilical arteries connect with each other at a distance of approximately 5 mm from the cord insertion in what is called the Hyrtl anastomosis.

[4] Resistance to blood flow decreases during development as the artery grows wider.

A portion remains open as a branch of the anterior division of the internal iliac artery.

A catheter may be inserted into one of the umbilical arteries of critically ill babies for drawing blood for testing.

[6] This is a common procedure in neonatal intensive care, and can often be performed until 2 weeks after birth (when the arteries start to decay too much).