What is the umbilical cord?

The umbilical cord connects a baby in the womb to its mother. It runs from an opening in your baby’s stomach to the placenta in the womb. The average cord is about 50cm (20 inches) long.

What does the umbilical cord do?

In the placenta, oxygen and nutrients from your bloodstream pass into your baby's bloodstream and are carried to your baby along the umbilical cord.

Blood circulates through vessels in the cord, which consists of:

• one vein that carries blood rich in oxygen and nutrients from you to your baby
• two arteries that return deoxygenated blood and waste products, such as carbon dioxide, from your baby back to the placenta

These blood vessels are enclosed and protected by a sticky substance called Wharton’s jelly, which itself is covered by a layer of membrane called the amnion.

Towards the end of your pregnancy, the placenta passes antibodies through the umbilical cord from you to your baby, giving it immunity from infections for about three months after birth. However, it only passes on antibodies that you already have.

What happens after the baby is born?

Soon after the birth, the midwife will:

• clamp the umbilical cord about 3-4cm (1½-2 inches) from your baby’s belly button with a plastic clip
• place another clamp at the other end of the cord, near the placenta

The cord will then be cut between the two clamps, leaving a stump about 2-3cm (1-1½ inches) long on your baby’s belly button. Your midwife will cut the cord or, with their agreement, you or your birth partner could do it.

There are no nerves in the cord, so cutting it isn’t painful for you or the baby. You can ask to have your baby lifted straight onto you before the cord is cut.

Between 5 and 15 days after your baby is born, the umbilical stump will dry out, turn black and drop off. After the stump comes off, it usually takes about 7-10 days for the belly button to heal completely.

Until the stump drops off and the belly button is completely healed, it’s important to keep the area clean and dry, to prevent infection.

Watch a video on taking care of your baby's umbilical stump.

Complications

If you notice any bleeding or discharge from your baby’s belly button, ask your midwife, health visitor or GP for advice.

After a baby is born, the midwife may take a sample of blood from the umbilical cord to:

• check the rhesus type of the baby’s blood
• test for sickle-cell anaemia

Occasionally, the umbilical cord has only one artery (single umbilical artery). This affects 0.2–1% of pregnancies. Its cause is not known. One artery can support an unborn baby through pregnancy and does not necessarily mean that there is a problem. However, it does increase the risk of the baby having problems that affect their heart, bones, intestines or kidneys.

Always speak to your midwife or GP if you are concerned about any aspect of your health when you are pregnant.