The umbilical cord, also known as funis, navel string or birth cord, forms the connecting link between the foetus and the placenta during pregnancy. It is centrally attached to the fetal surface of the placenta with the umbilicus of the fetus. It allows the fetal blood to flow to and from the placenta.
The umbilical cord carries nutrition and oxygen from the placenta to the foetus.
Development of the umbilical cord
The umbilical cord is developed from the connective stalk or body stalk of mesodermal tissue stretching between embryonic disc and chorion shown in the figure below-
Characteristics of the umbilical cord
The umbilical cord is bluish-white in colour, about 50 cm in length with a usual variation of 30-100 cm. Its average diameter is 1.5 cm with a variation of 1-2.5 cm.
The thickness of the cord is not uniform. There is the presence of nodes or swellings at some places due to the dilatation of umbilical veins or collection of Wharton’s jelly. These swellings are also called false knots.
The umbilical cord shows the spiral twist from left to right due to the spiral turn taken by the umbilical vessels- vein around the arteries. Initially, there are four vessels- two arteries and two veins. Out of the two umbilical veins, the right one disappears by the 4th month and leaves behind one vein which carries oxygen blood from the placenta to the foetus. In fetal congenital abnormalities, there is a single umbilical artery present.
Functions of the umbilical cord
The umbilical cord acts as a lifeline between the placenta and the foetus supplying oxygen and nutrients to the foetus and removing waste products. Exchange of fluid and electrolyte also take place between umbilical vessels and the amniotic fluid.
Approximately 400 ml/minute of blood flows through the umbilical cord. It has no pain receptors so cutting the cord after delivery is painless. About 1-1.5 inches of cord is kept behind while cutting the cord after childbirth.
Abnormalities of the umbilical cord
Some of the abnormalities of the cord are-
- Short cord– Cord length is too short, less than 30 cm which might cause abruption placenta and uterine inversion. Common in breech presentation.
- Long cord– It is more than 100 cm or can be as long as 300 cm and can prolapse during the childbirth process. It can develop a true knot due to its long length.
- True knot- Rare one and occurs in 1% pregnancies with increased risk of perinatal loss. It is more common in mono-amniotic twins.
- False knot– It is the developmental variation that occurs due to an accumulation of Wharton’s jelly.
- True cyst – Occurs due to the remnant of umbilical vesicle or of allantois (a blind tubular structure may present near the fetal end which is continuous inside the foetus with its urachus and bladder).
- False cyst– It forms due to liquification of Wharton’s jelly.
Loops of the umbilical cord
During pregnancy, there are chances of development of loop of cord around fetal’s neck which endangers the baby’s life, if it is too tight. It has to be diagnosed during pregnancy by ultrasound; so that, precautionary measures can be taken at the time of delivery to save the life of the baby. Loops of the umbilical cord are of three types-
- One loop of cord around fetal neck (21%)
- Two loops of cord around fetal neck (3.5%)
- Three loops of cord around fetal neck (0.2%). Very rare one.
Early diagnosis of the loop of the cord is very necessary to prevent any complications.
In the above post, we discussed the umbilical cord, its development, characteristics, functions, abnormalities and loops of the cord.