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Obstetrics Simplified - Diaa M. EI-Mowafi

The Umbilical Cord

Anatomy

Origin: It develops from the connecting stalk.

Length: At term, it measures about 50 cm.

Diameter: 2 cm.

Structure: It consists of mesodermal connective tissue called Wharton's jelly, covered by amnion. It contains:

  • one umbilical vein carries oxygenated blood from the placenta to the foetus,
  • two umbilical arteries carry deoxygenated blood from the foetus to the placenta,
  • remnants of the yolk sac and allantois.

Insertion: The cord is inserted in the foetal surface of the placenta near the center "eccentric insertion" (70%) or at the center "central insertion" (30%).

Abnormalities of the Umbilical Cord

Abnormal cord insertion

  • Marginal insertion: in the placenta (battledore insertion).
  • Velamentous insertion: in the membranes and vessels connect the cord to the edge of the placenta. If these vessels pass at the region of the internal os, the condition is called " vasa praevia". Vasa praevia can occur also when the vessels connecting a succenturiate lobe with the main placenta pass at the region of the internal os.

Abnormal cord length

Short cord which may lead to:

  • intrapartum haemorrhage due to premature separation of the placenta,
  • delayed descent of the foetus during labour,
  • inversion of the uterus.

Long cord which may lead to:

  • cord presentation and cord prolapse,
  • coiling of the cord around the neck,
  • true knots of the cord.

Knots of the cord

  • True knot: when the foetus passes through a loop of the cord. If pulled tight, foetal asphyxia may result.
  • False knot: localised collection of Wharton’s jelly containing a loop of umbilical vessels.

Torsion of the cord

It may occur particularly in the portion near the foetus where the Wharton's jelly is less abundant.

Haematoma

Due to rupture of one of the umbilical vessels.

Single umbilical artery

It may be associated with other foetal congenital anomalies.

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