Your baby's umbilical cord

What is the umbilical cord?

During pregnancy, the umbilical cord is your baby’s lifeline to the placenta, the pancake-shaped organ attached to your uterus. It delivers vital nutrients from your body to your baby, and ferries away the waste products your baby produces. The umbilical cord starts to form at about 4 weeks of pregnancy.

The umbilical cord is surprisingly thick and tough, and typically measures about 20 inches long and 1 inch in diameter. It contains three blood vessels: one vein that carries nutrients and oxygen-rich blood from your circulatory system to your baby, and two arteries that deliver waste products and oxygen-depleted blood back to you. Your kidneys process your baby’s wastes along with yours for disposal and your lungs replenish the blood with oxygen. 

Cutting the umbilical cord

Soon after your baby is delivered, it’s time to clamp and cut the cord. Your partner or labor support person can cut the cord themselves, if they'd like.

First, your practitioner uses two special clamps to close the cord shut, usually in two places about one inch apart. It takes a bit of effort to cut through the thick, rope-like cord, but not to worry: There aren’t any nerves in the cord, so this procedure is painless for your baby (and for you).

When does the umbilical cord fall off?

Once the cord is cut, a small umbilical cord stump is left behind. This piece of tissue eventually dries up and falls off in one to three weeks. Until it does, you’ll need to keep it clean and dry. Find out more about caring for your baby's umbilical cord stump. 

Of course, your baby will carry a small remnant of the time they spent attached to you: their belly button! You have no control over whether your baby ends up with an innie or an outie. How your baby's belly button looks depends on how the umbilical cord was attached to your baby’s belly during pregnancy, and it can change over time as your child grows.

Delayed cord clamping

Traditionally, practitioners in the United States cut the baby's umbilical cord almost immediately after birth, but research shows that delayed umbilical cord clamping has health benefits, particularly if your baby is born prematurely.

Waiting to clamp the cord allows the blood in the cord to continue to flow to your baby, lowering the risk of newborn anemia and iron deficiency in infancy.

Umbilical cord blood banking

You might want to consider banking your baby's cord blood. Cord blood contains stem cells that can grow into different kinds of body cells and have been used to treat certain diseases, including some cancers and blood disorders.

For a yearly fee (plus the cost of collecting the cord blood), you can store some of your baby’s cord blood in a private bank for future use by her or other family members. Or you can donate your baby’s cord blood to a public bank, where it remains available to anyone who needs it and who matches your baby’s blood type.

Keep in mind that you’ll need to decide what you want to do well in advance of your baby’s birth so that all the necessary arrangements can be made. Here's a rundown of everything you need to know about cord blood banking.

Umbilical cord abnormalities

Some conditions can arise during pregnancy and delivery that affect the umbilical cord. Most of the time, they resolve on their own and don’t harm your baby. A few, however, can be serious. The most common umbilical cord conditions include the following:

Nuchal cord

The umbilical cord may be wrapped around the baby’s neck during delivery. This condition is actually quite common. In most cases, the cord is simply untangled from the baby’s neck once the head is out, and delivery proceeds normally. But if the cord is wrapped very tightly, your healthcare provider may need to clamp and cut it before the baby’s shoulders are delivered.

Umbilical cord compression

This occurs when the cord becomes constricted, cutting off a baby’s oxygen supply. The cord may have become knotted or tangled, which can happen if it’s unusually long or if the baby’s head is pressing on it during delivery. Umbilical cord compression usually can be detected during labor by changes in the baby’s heart rate. A technique called amnioinfusion, in which fluid is inserted into the uterus through a thin tube, may help take the pressure off the cord and allow delivery to proceed normally.

Umbilical cord prolapse

This is a serious delivery complication: A cord prolapse means the umbilical cord comes out of the vagina as the baby’s head is delivered, which can cut off blood flow to the baby. An emergency c-section is usually performed in such cases. 

Single umbilical artery

A very small number of babies have only one umbilical artery instead of two. This condition occurs more often when the woman is carrying two or more babies. Having only one umbilical artery can cause problems for the baby’s digestive organs, kidneys, and heart. If you’re diagnosed with this condition during pregnancy, you’ll have special tests to monitor your baby’s health along the way.

Umbilical cord cysts

These are pockets of fluid that form in the cord. One type, called a true cyst, is harmless and often goes away on its own before the baby is born. It’s usually discovered during a first-trimester ultrasound. However, cysts that are found later in the pregnancy may indicate a genetic condition or other problem. If this type of cyst is found, your healthcare provider will likely recommend a detailed ultrasound exam and genetic testing.

Velamentous cord insertion

Velamentous cord insertion and marginal cord insertion mean that the umbilical cord is attached to the amniotic membrane or the side of the placenta rather than going right into the center of the placenta as usual. This leaves the vessels of the cord more exposed than they would be if they were attached directly into the placenta, where they would be protected by a gel-like substance called Wharton's jelly.

Vasa previa

In vasa previa, some of the fetal blood vessels are exposed and cross over the cervical opening, instead of being contained in the umbilical cord. When contractions happen, these blood vessels stretch and may rupture, resulting in catastrophic fetal blood loss and fetal distress. This is a very serious condition and may require prolonged monitoring in the hospital.