Embryology · Fetal period, placenta and twins
Umbilical cord: two arteries, one vein !
- Embryonic structure
The cord joins the fetus to the placenta. It carries two arteries and one vein wrapped in a jelly that protects them.
Updated 2026-11-01
See it in 3D: Falciform ligament · Liver · Urinary bladder
What it is
The umbilical cord forms when the amnion wraps the connecting stalk and the vitelline duct. At term it holds two umbilical arteries, which carry poorly oxygenated blood to the placenta, and one umbilical vein, which brings oxygenated blood to the fetus, all in Wharton's jelly. Counting its vessels is part of the ultrasound and the newborn exam.
Structure
- Week 5: the connecting stalk (allantois and umbilical vessels), the vitelline duct and a canal to the chorionic cavity pass through the primitive umbilical ring.
- The growing amnion wraps these elements and forms the primitive umbilical cord.
- At the end of month 3 the intestinal loops return to the abdomen and the vitelline duct and canal close off.
- At term it is about 50 to 60 centimetres long and about 2 centimetres across.
What it becomes
- Umbilical vein: round ligament of the liver (ligamentum teres), in the free edge of the falciform ligament.
- Umbilical arteries: the distal part forms the medial umbilical ligaments; the proximal part stays as the superior vesical arteries.
- Allantois: urachus, then the median umbilical ligament.
- Vitelline duct: closes off; if it persists, it gives Meckel diverticulum or other remnants.
- The cord stump dries and falls off in one to two weeks, leaving the umbilicus.
Clinical notes
- Velamentous insertion and vasa previa: unprotected vessels that can tear in labour and cause fetal haemorrhage.
- Long cord: prolapse, nuchal loops and true knots; short cord: traction and risk of abruption.
- Patent urachus: urine leaks from the umbilicus; patent vitelline duct: intestinal contents leak.
- The newborn's cord vessels are counted: a single umbilical artery prompts a search for other anomalies.
Test yourself
Think of the answer, then tap the question to see it.
How many arteries and veins does a normal umbilical cord have, and what blood does each carry?
Two arteries, carrying deoxygenated blood from the fetus to the placenta, and one vein, carrying oxygenated blood from the placenta to the fetus.
What does a single umbilical artery mean?
It is a common finding linked to renal, cardiac and chromosomal anomalies; it prompts a detailed ultrasound and a search for other defects.
What adult structure does the umbilical vein become?
The round ligament of the liver, which runs in the free edge of the falciform ligament.
Which tissue surrounds and protects the cord vessels?
Wharton's jelly, a mucous connective tissue rich in extracellular matrix.
See it in 3D
The structures of Durgical's 3D anatomy where it is found.
Related
- Placenta: structure, circulation and functions
- Fetal circulation and the changes at birth
- Fetal membranes: amnion, chorion, yolk sac and allantois
- Meckel diverticulum and other vitelline duct remnants
- Urachal anomalies: patent urachus, cyst and sinus
- Midgut: physiological herniation and rotation
Related conditions
Educational content on embryonic development; not a guide to prenatal diagnosis or to medicines in pregnancy and no substitute for a health professional's advice. No doses are given.
Sources: Umbilical cord conditions | March of Dimes (March of Dimes, 2016); Langman's Medical Embryology, 13th ed., ch. 8: Third Month to Birth: The Fetus and Placenta (Wolters Kluwer, 2015).
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Representative model, for educational purposes only.