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The umbilical cord is the lifeline that connects the fetus to the placenta providing life support through passage of nutrients, oxygen, and waste products to and from the fetus. It consists of three vessels, two arteries, and a vein, running in a spiral arrangement with a length of about 50 to 60 cm at term. It is lined on the inside with the thick myxomatous Wharton jelly and covered on the outside by a single layer of amnion providing protection to the cord from direct compression, kinking, and traction. The circulation in the umbilical cord is the reverse of the adult in that the vein carries the oxygenated blood to the fetus, and the arteries bring venous blood back to the placenta. Normally, the cord inserts into the center of the placenta.

Cords have been reported to measure as short as 0 cm and as long as 104 cm. It appears that the length of the umbilical cord is determined at least partly by the amount of amniotic fluid present in the first and second trimesters of pregnancy and on the mobility of the fetus. If there is oligohydramnios, amniotic bands, or limitation of fetal movement for any reason, the umbilical cord will not develop to an average length. A short cord may result in delay in descent of the fetus, fetal distress, and separation of the placenta from the wall of the uterus, inversion of the uterus, and rupture leading to hemorrhage and possible fetal exsanguination. On the other hand, a long cord is subject to entanglement, knotting, encirclement of the fetus, and prolapse.

When the cord is absent, the fetus is attached directly to the placenta at the umbilicus. Body stalk anomaly is seen accompanying the absent cord. Amniotic band syndrome is associated with the pathogenesis.


Umbilical cord has characteristic screw-shaped coils with average of 11 loops or turns along its length. The coiling level can be objectively presented by the umbilical coiling index (UCI), which is the number of coils in the cord divided by cord length in cm. It is referred to as hypocoiled if the UCI is below the 10th percentile and hypercoiled if it is above 90th percentile. It is thought that cord coiling plays a role in protecting the umbilical cord from external pressure such as stretching, tension, and entanglement. There is a strong association between UCI and adverse pregnancy outcome including intrauterine growth restriction. Both hypocoiled and hypercoiled cords were associated with increased risk of preterm birth, need for intervention delivery for nonreassuring fetal heart rate, and meconium-stained amniotic fluid. There is a strong association between hypercoiled cord with intrauterine demise.

Single Umbilical Artery (SUA)

SUA is a variation in the umbilical cord anatomy in which there is only one umbilical artery. It is the ...

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