Single umbilical artery: What does a two-vessel cord mean in pregnancy?
A single umbilical artery, often called a two-vessel cord, means that the umbilical cord has only two blood vessels—one vein and one artery—instead of the usual three. This is typically discovered during a pregnancy ultrasound and can be a source of concern for parents. It's important to know that a single umbilical artery (SUA) does not always pose a risk to the baby, but it does require careful monitoring.
SUA is usually diagnosed unexpectedly, since the umbilical cord structure isn't closely examined in early pregnancy. During the second trimester ultrasound, specialists count the vessels in the cord. If only two are seen, your doctor may suggest further tests to rule out any related conditions.
What is a single umbilical artery (SUA)? 🧬
The umbilical cord normally contains three vessels: two arteries that carry waste and carbon dioxide away from the baby, and one vein that brings oxygen-rich blood back. With SUA, only one artery is present, which is a variation in fetal circulation.
This occurs in about 0.5–1% of pregnancies. SUA itself is not a disease, but an anatomical difference. Its significance depends on whether it is associated with other fetal anomalies.
How is a two-vessel umbilical cord found?
Single umbilical artery is most often detected during the 18–22 week ultrasound, when the baby's organs and umbilical cord are examined in detail. The sonographer checks a cross-section of the cord and counts the vessels.
If only two vessels are visible, your doctor will inform you and may recommend further tests, such as a detailed fetal heart ultrasound or genetic screening.
What does SUA mean for the baby?
In most cases, a single umbilical artery does not cause problems. Most babies with SUA develop normally and are born healthy. However, SUA can sometimes be linked to other developmental differences, such as heart, kidney, or chromosomal conditions.
For this reason, doctors recommend closer monitoring to catch any additional concerns early.
Practical examples: What does monitoring look like?
- Regular ultrasounds: Your baby's growth, organ development, and blood flow are checked more often.
- Genetic counseling: If other findings are present, genetic consultation may be suggested.
- Fetal heart ultrasound: A detailed scan of the baby's heart helps rule out heart defects.
- Postnatal checks: After birth, the pediatrician will examine your baby's organs and development.
Possible risks and associations
SUA alone does not automatically mean danger, but it can be associated with:
- Lower birth weight
- Growth restriction
- Kidney or heart development differences
- Chromosomal anomalies (rarely)
Most babies with SUA are completely healthy, and pregnancies often progress normally.
Medical background: Why does SUA happen?
The umbilical cord vessels develop early in pregnancy. Sometimes, one artery does not form or regresses. The exact cause is often unknown, but genetic and environmental factors may play a role.
SUA is not inherited and is not caused by parental lifestyle or choices. In most cases, it happens by chance.
When should you see a doctor? 🚩
If SUA is found during ultrasound, your doctor will explain the next steps. See your doctor if:
- Additional findings are noted on ultrasound
- Your baby's growth slows down
- You notice unusual symptoms (like decreased fetal movement)
- You feel uncertain or worried
Regular checkups help detect any problems early.
What can you do as a parent if SUA is diagnosed?
- Ask questions: Your doctor is there to answer and help you understand.
- Follow recommended tests: Regular monitoring provides reassurance.
- Track fetal movements: Report any changes to your doctor.
- Seek support: Connect with other parents or professionals if you need help.
Supportive thoughts during pregnancy 💚
A single umbilical artery diagnosis can bring uncertainty and worry, but most babies with SUA grow and develop well. Regular medical checkups, professional support, and reliable information help you feel confident throughout your pregnancy.
If you have more questions or want additional trustworthy guides, our app offers further helpful resources. Remember: every question matters, and you are not alone on this journey.