Structure & Function
The umbilical cord forms around the fifth week of pregnancy and can grow up to 20 inches long at full-term. It is a tough, sinewy structure with two main layers: an outer layer of smooth muscle, and an inner layer containing a gelatinous fluid called Wharton's jelly. There are typically three vessels within this substance: one vein and two arteries. The vein carries oxygen and nutrient-rich blood from the placenta to the fetus, and the arteries carry deoxygenated and nutrient-depleted blood away from the fetus.
The umbilical cord enters the fetus through the abdomen and turns into two branches: one joins with the hepatic portal vein in the liver, and the other connects to the heart through the inferior vena cava. These two branches form a circuit in the fetus's body and reconnect to the umbilical cord outside. In rare cases, the umbilical cord may not develop correctly, or some other problem occurs during birth. Sometimes these problems can be detected via ultrasound before birth, but in many cases, they are not noticed until after the baby is born. Let's look at some of these potential issues and how they can affect the baby.
Potential Problems
- Single umbilical artery: In rare cases, the umbilical cord may form with a missing artery. The cause of this is unknown, but it can lead to birth defects, including problems with the heart, nervous system, chromosomes and urinary tract. This problem can be detected before birth.
- Umbilical cord prolapse: As the baby passes through the birth canal, the umbilical cord may prolapse, or slip into the birth canal, and become compressed by the baby during delivery. This can cut off the baby's blood supply and become a life-threatening condition if the baby is not delivered immediately.
- Umbilical cord knots: It is not uncommon for the cord to become wrapped around the baby's neck, but this rarely causes serious problems. In rare cases, however, it may become tied in knots, and this can cut off the baby's blood supply.
- Umbilical cord cysts: Sometimes cysts can be seen developing on the umbilical cord via ultrasound. This can lead to abnormalities in the kidneys, chromosomes and abdomen.
- Vasa previa: In rare cases, umbilical cord blood vessels may shift outside of the protection of the cord and move underneath the baby. This can lead to tears in the vessels and life-threatening bleeding. Pregnant women who experience bleeding in the second or third trimester should seek medical attention to rule out this complication.
Cord Blood Storage
The blood inside the umbilical cord is called cord blood, and it contains undifferentiated (blood-forming) stem cells. This blood can be removed from the cord and stored in private or public banks with the intention of treating illnesses like leukemia and sickle cell anemia. Some parents decide to store this blood in a private bank in case the child or a family member needs the stem cells later in life. Private banking is the subject of some controversy. Many medical professionals discourage storage for self-use because most health conditions will already be present in the cord blood, and it is highly unlikely that the child will actually use the cells. Additionally, it is a very costly practice compared to public banking.
Given the controversy and concern surrounding private banking, there is some promise in the storage and use of cord blood in public banks. These banks collect donations for public use, and donated stem cells are already being used to save lives. For example, if there is a difficulty finding a bone marrow donor for a child with leukemia, these cells can be transplanted, effectively increasing the donor pool. Researchers are currently studying the many potential uses of these cells.
Lesson Summary
The umbilical cord is a tube-like structure that connects a fetus to the mother's placenta. A placenta is an organ attached to the uterine wall with access to the mother's blood supply. The cord contains one vein and two arteries, housed within its protective Wharton's jelly. The vein carries oxygenated blood and nutrients from the placenta to the fetus through the abdomen, and the arteries remove waste products. We examined some potential problems that can occur with the umbilical cord, including the single umbilical artery, umbilical cord prolapse, umbilical cord knots, umbilical cord cysts, and vasa previa. We also noted that stem-cell rich cord blood, which is the blood inside the umbilical cord, is gaining attention due to its potential for treating blood-related diseases. Finally, we explored the practice of cord blood storage in private versus public banks.
Umbilical Cord Study Guide
- Umbilical cord: a tube that connects a fetus to its mother placenta
- One vein that transports nutrients and oxygen
- Two arteries that remove waste
- Wharton's jelly: protects the vein and two arteries
- Placenta: an organ attached to the uterine wall that connects to the mother's blood supply
- Cord blood: contains stem cells that may help treat diseases of the blood
- Public cord blood bank: Donated stem cells for public use; already saving lives
- Private cord blood bank: Stored stem cells for private use; rarely used during the lifetime of the owner
| Umbilical Cord Disorder |
Description |
Prognosis |
| Single Umbilical Artery |
The cord is missing an artery |
Birth defects in the heart, nervous system, chromosomes and urinary tract |
| Umbilical Cord Prolapse |
The cord slips into the birth canal and compresses |
Life-threatening unless baby is delivered immediately |
| Umbilical Cord Knots |
The cord forms knots |
Can cut off baby's blood supply |
| Umbilical Cord Cysts |
Cysts develop in the cord |
Abnormalities in the kidneys, chromosomes and abdomen |
| Vasa Previa |
Umbilical blood vessels shift out of cord and tear |
Life-threatening bleeding |
Learning Outcomes
Now that you've finished the lesson, you're ready to:
- Define the umbilical cord and state its purpose
- Outline the structure of the umbilical cord
- Discuss some of the complications that can develop within the umbilical cord
- Compare the options for umbilical cord blood storage
Medical Disclaimer: The information on this site is for your information only and is not a substitute for professional medical advice.
