What Is an Umbilical Cord?
Quick Answer
The umbilical cord is a flexible, rope-like tube that connects a baby to its mother while it grows inside the uterus. It carries food and oxygen from the mother to the baby and takes away waste the baby does not need. After the baby is born, the cord is cut, and the small piece left behind dries up and falls off, leaving the belly button.
Explaining By Age Group
Ages 3-5 Simple Explanation
You know how a straw lets you drink juice from a cup? The umbilical cord is kind of like a straw that connects a baby to its mommy while the baby is growing inside! It brings yummy food and fresh air from the mommy right to the baby so the baby can grow big and strong.
You know how plants get water through their stems? The baby gets what it needs through the umbilical cord in a similar way. The cord goes from the baby's tummy all the way to something called the placenta, which is attached to the mommy. It is the baby's special food delivery system!
You know how when you are done with a straw, you do not need it anymore? When the baby is born and can eat and breathe on its own, it does not need the umbilical cord anymore either! The doctor cuts the cord, and it does not hurt the baby or the mommy at all -- not even a tiny bit.
You know what is left behind after the cord is cut? Your belly button! Everyone has a belly button because everyone was once connected to their mommy by an umbilical cord. Whether your belly button goes in or sticks out, that is where your cord used to be when you were a tiny baby!
Ages 6-8 More Detail
The umbilical cord is a soft, flexible tube that connects a growing baby to its mother while the baby is inside the uterus. One end of the cord is attached to the baby's belly, and the other end is attached to the placenta, which is an organ stuck to the wall of the mother's uterus. The cord is usually about 20 inches long and looks a bit like a twisted, rubbery rope.
The cord has a very important job: it carries everything the baby needs to live and grow. Blood rich in oxygen and nutrients flows from the mother through the placenta and into the umbilical cord, and then into the baby's body. At the same time, blood carrying waste (like carbon dioxide) flows from the baby back through the cord to the placenta, where the mother's body gets rid of it.
Inside the umbilical cord, there are three blood vessels: two small arteries and one larger vein. The vein carries fresh blood with oxygen and food from the placenta to the baby. The two arteries carry used blood back from the baby to the placenta. A jelly-like substance surrounds the blood vessels to protect them and keep the cord from getting squished.
When the baby is born and starts breathing air and eventually drinking milk, it no longer needs the umbilical cord. A doctor or nurse clamps the cord in two places and cuts between the clamps. There are no nerves in the cord, so the baby does not feel any pain at all when it is cut.
After the cord is cut, a short stump is left attached to the baby's belly. Over the next week or two, the stump dries out, shrivels up, and falls off on its own. What is left behind is the belly button! Some belly buttons are "innies" (they go inward) and some are "outies" (they stick out a little). Either way, your belly button is a reminder of the cord that kept you fed and healthy before you were born.
Ages 9-12 Full Explanation
The umbilical cord is the lifeline between a developing baby and its mother during pregnancy. It is a flexible, tube-like structure that typically grows to be about 20 inches long and about half an inch to an inch thick. One end attaches to the baby's abdomen (where the belly button will later be), and the other end connects to the placenta, which is an organ embedded in the wall of the mother's uterus. The cord begins forming around the fifth week of pregnancy and functions until the moment the baby is born.
The cord's main job is to transport blood between the baby and the placenta. Inside the cord, there are three blood vessels: one large vein and two smaller arteries. The vein carries oxygen-rich, nutrient-packed blood from the placenta to the baby, providing everything the baby needs to grow -- sugars, fats, proteins, vitamins, and oxygen. The two arteries carry blood from the baby back to the placenta. This returning blood contains carbon dioxide and other waste products that the baby's body needs to get rid of. The placenta then passes this waste into the mother's bloodstream, and her body removes it.
The blood vessels inside the cord are surrounded and protected by a thick, jelly-like substance called Wharton's jelly. This jelly acts as padding, keeping the vessels from being compressed or kinked. The cord also has a slight natural twist to it, which helps keep it strong and flexible. In rare cases, the cord can become knotted or wrapped around the baby, but doctors monitor for this during pregnancy and delivery to make sure the baby stays safe.
After the baby is born and takes its first breaths, its lungs take over the job of getting oxygen and its digestive system will soon handle nutrition from milk. The umbilical cord is no longer needed. A medical professional clamps the cord in two places and cuts between the clamps. Since the cord contains no nerve fibers, neither the mother nor the baby feels any pain during this process.
A small stump of the cord remains attached to the baby's belly after it is cut. Parents are instructed to keep the stump clean and dry. Within one to three weeks, the stump dries out, turns dark, and falls off naturally, leaving behind the belly button (also called the navel). Whether a person ends up with an innie or an outie belly button depends on how the skin heals around the area where the cord was attached -- it has nothing to do with how the cord was cut.
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Tips for Parents
An umbilical cord can be a challenging topic to discuss with your child. Here are some practical tips to help guide the conversation:
DO: Use correct anatomical terms. Teaching children the real names for body parts (penis, vagina, uterus) removes shame and gives them vocabulary to communicate clearly, including about safety.
DON'T: Don't make it awkward. Your comfort level sets the tone. If you treat it as a natural, normal topic, your child will too. If you're visibly uncomfortable, they'll learn that bodies and reproduction are embarrassing.
DO: Answer only what they're asking. A 4-year-old asking 'Where do babies come from?' might be satisfied with 'Babies grow in a mommy's tummy.' You don't need to explain conception unless they ask.
DO: Use books as aids. There are excellent age-appropriate books about reproduction and bodies. Reading together can make the conversation feel more natural and provide helpful illustrations.
DON'T: Don't use stork stories or seed metaphors that you'll have to 'unlearn' later. Simple, truthful answers build a foundation of trust that serves your child through puberty and beyond.
Common Follow-Up Questions Kids Ask
After discussing an umbilical cord, your child might also ask:
Does it hurt when the umbilical cord is cut?
No, not at all! The umbilical cord does not have any nerve endings, so neither the baby nor the mother feels any pain when it is cut. It is similar to cutting a fingernail -- there is no sensation in the cord itself.
Why do we have belly buttons?
Your belly button is the spot where the umbilical cord was attached when you were growing inside your mother. After you were born and the cord was cut, a small stump was left. When that stump dried up and fell off, it left behind your belly button. Everyone has one because everyone was connected to their mother by an umbilical cord!
What makes a belly button an innie or an outie?
Whether you have an innie or outie belly button depends on how the skin and tissue healed after the umbilical cord stump fell off. It is not determined by how the doctor cut the cord. Most people have innies, and about 10 percent have outies. Both are completely normal.
What is the placenta?
The placenta is a special organ that grows inside the mother's uterus during pregnancy. It attaches to the uterine wall and connects to the baby through the umbilical cord. Its job is to filter nutrients and oxygen from the mother's blood and send them to the baby. After the baby is born, the placenta is also delivered -- it is no longer needed.
How long is the umbilical cord?
The average umbilical cord is about 20 inches (50 centimeters) long, though it can range from shorter to longer depending on the pregnancy. It needs to be long enough for the baby to move around comfortably inside the uterus without pulling on the placenta.
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