How The Umbilical Cord Works And What You Should Know About It

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In the earliest days of pregnancy, much changes inside your body—even before you begin to feel it. One of the most fascinating developments is the formation of the umbilical cord. It is often called your baby’s lifeline, as it supplies all the nutrients to the growing baby or fetus.

The umbilical cord forms during the fifth week of pregnancy, although its foundation starts earlier. At first, your embryo is connected to the yolk sac, which provides early nutrients. But as the placenta grows and takes over, the umbilical cord becomes the bridge between you and your baby.

How the Umbilical Cord Works

This cord is not just a single tube. It’s made up of three blood vessels—two arteries and one vein. The vein carries oxygen-rich blood and nutrients from you to your baby. The two arteries take waste products and carbon dioxide from your baby back to your body, where they are disposed of naturally.

These vessels are surrounded by a jelly-like substance called Wharton’s jelly. It cushions and protects the cord, keeping it from getting compressed as your baby moves. The cord is covered in a thin layer of skin early on, which later becomes part of the amniotic membrane.

Despite its delicate look in ultrasound images, the umbilical cord is strong. It twists and coils, which is normal and even helpful.

You won’t feel the cord growing, but it plays a constant role in every moment of your pregnancy. Through it, your baby receives glucose for energy, amino acids for building tissues, and immune cells to help fight infection.

By the end of your first trimester, the cord has grown to about 20 to 24 inches. It stretches and adapts as your baby grows, allowing freedom of movement in the womb.

What You Should Know in Early Pregnancy

Rare complications can involve the cord, like knots or cord insertions that are not in ideal locations. These are usually picked up on routine scans later in pregnancy and are often harmless, though some need extra monitoring.

One common question many women ask is whether anything they do can damage the cord. The good news is: no. The cord is protected inside the uterus, and daily activities, sleep positions, or gentle exercise won’t harm it. However, staying healthy overall—eating well, managing stress, and avoiding smoking—does support cord health as part of a healthy pregnancy.

Later in pregnancy, the cord may be discussed more during scans or delivery planning, especially if it wraps around the baby’s neck. In most cases, even that doesn’t pose a serious risk and is managed safely by your care team.

But in these early weeks—from week one through week ten—it’s enough to simply know this: while you’re beginning to imagine life as a parent, the umbilical cord is already doing the quiet work of nourishing new life.

It’s working long before you can feel a kick or hear a heartbeat. And that’s something truly extraordinary.