Umbilical cord – what happens after it is cut?

During pregnancy, the umbilical cord is a baby’s lifeline – then it is cut. What happens inside mother and baby? “It was like a thick, elastic cable. It took me force to cut through it!” That’s how my husband romantically described cutting the umbilical cord after the birth of our daughter. But what happens after cutting it? When Tom asked me this over dinner a few days ago – as one does when sitting together for family dinner… – we concluded that we actually had no idea. For nearly nine months, the umbilical cord nurtures the baby, then it is cut. But what happens inside baby and mum? Does the blood continue to circulate through the blood vessels? And if so, why don’t we bleed internally as a result? Once again a reason to do some research… and the result surprised me!


A string used to be enough for clamping the cord, now we use clamps. (Points in Nursing, 1910, Emily A. M. Stoney)

On the mom’s side, the umbilical cord is connected with the placenta. The placenta develops pregnancy and delivers vital nutrients and oxygen for the baby through its blood vessels. A quarter to half hour after birth, the placenta is delivered as afterbirth, and so also the remaining maternal side of the umbilical cord is delivered.

Diagram of the placenta and umbilical cord (right). Umbilical arteries and umbilical vein connect the circulation of mother and baby. (Henry Vandyke Carter – Henry Gray (1918) Anatomy of the Human Body Gray’s Anatomy, plate 39)


To understand what happens on the baby’s side, we have to take a closer look at the umbilical cord. Unlike what we might imagine, the umbilical cord does not consist of muscles or connective tissue, but of a special jelly-like substance, the Wharton’s jelly. A vein running through it transports oxygen-rich blood from the mother to the fetus, while two arteries return the blood and breakdown products back from the baby to the mother. As soon as the baby is born and breaths, the umbilical cord has fulfilled its function. The arteries constrict and the blood flow to the mother ends. And while it is cozy and warm inside the mother, the cold of the outside world causes the Wharton’s jelly to induce the vein’s collapse. The blood now only circulates within the baby, even when the umbilical cord is not clamped. (Lotus birth is a birth in which the umbilical cord is not cut and left on the baby together with the placenta. After three to ten days, the umbilical cord falls off.)

Remainders of the umbilical vein and arteries remain with us after birth, in a different form. The closed vein becomes a fibrous cord, the round ligament of the liver. Blood keeps flowing in parts of the umbilical arteries: while the area close to the navel closes off to become the medial umbilical ligament, the rest remains open and forms part of the blood supply to bladder and seminal duct.

 After the umbilical cord falls off, the remaining belly button reminds us of our connection to our mother. And if with all the navel gazing you’ve found some belly fluff, rest assured – its origins have been solved. More on this maybe later, or at the modern source of knowledge, Wikipedia.

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