Umbilical Cord
Supplies Blood, Oxygen And Nutrients To Your Baby

Pregnancy Guidelines

picture of umbilical cord in womb

Umbilical Cord

Contents

What Is The Umbilical Cord?
How Long Is The Cord?
Umbilical Cord Complications




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Pregnancy Guide
What Is The Umbilical Cord?

The umbilical cord forms the major connection (supply-line) between the fetus and the placenta. It is a ropelike structure whose main function is to carry supplies of oxygen and nutrients to the growing fetus and to take away waste products dumping them back in the mother’s blood supply. After delivery the cord is clamped and then cut about 2.5cm away from the baby’s abdomen. The stump falls off after a few weeks leaving a permanent scar - the belly button.

The umbilical cord consists of:

Wharton's jelly: A jelly like substance which protects and insulates the blood vessels running through the cord. When exposed to air it naturally collapses causing a sealing effect - within 5 minutes of childbirth the cord would naturally seal if the doctor did not clamp it.
Blood vessels: At first there are 4 in number - 2 arteries and 2 veins. By the third month, there are 3 in number when the umbilical veins fuse leaving one single vein. The vein carries oxygenated blood and nutrients to the fetus from the mother’s blood supply. The two arteries transport waste from the baby to the placenta where it is passed back into the mother’s blood supply for excretion by her kidneys.
Umbilical vesicle and its duct: the shriveled remnant of the yolk sac, may be found as a very small yellow body near the attachment of the cord to the placenta. This sac was important in the first few weeks of development for nourishing the embryo, but usually shrivels up by week 7.

How Long Is The Cord?

The cord on average is about 50 cm in length, but its length varies greatly, and may be as long as 180 cm, or as short as 7.5 cm. It is about 1 cm thick, but is not uniformly so - it has nodes or swellings in part which are sometimes caused by dilatation of the umbilical vein, but more often by thicker pockets of Wharton's jelly. At the earliest stage the cord is straight, but as early as the 12th week it shows a spiral twist.

Umbilical Cord Complications

Knots In The Cord
In addition to the nodes mentioned above (sometimes called false knots) on rare occasions the cord has one or more real or true knots, due to the fetus passing through a loop in the cord. Literally the fetus can tie itself up in knots. If a true knot becomes drawn very tight the fetus can die from obstruction to its blood supply. The risk is increased by multiple births because the cords of the babies can become entangled. This is not the same condition as a cord being coiled around the baby’s neck (nuchal cord). With a nuchal cord nutrients can still flow through the cord as it is not pulled tightly, so this sort of complication rarely gives rise to any serious trouble.

Short Cord
If the cord is abnormally short it can cause premature separation of the placenta (placenta abruption) or inversion of the uterus, but this sort of incidence is rare.

Abnormal Insertion Of The Cord Into The Placenta
The cord is usually attached to the centre of the placenta, but sometimes it is attached to the edge of the placenta (known as battledore placenta). This doesn't cause any problems. In rare cases the cord is attached to the membranes of the placenta, rather than the placenta itself (velamentous insertion of the cord). This is highly dangerous because the veins of the cord are exposed, they are not protected by the Wharton jelly and so are prone to rupturing (vasa praevia). If the blood vessels rupture, the mother will experience vaginal bleeding and the baby will develop an irregular heartbeat and even eventual death due to lack of blood supply. The risk of mortality of the fetus is about 60 percent.

Single Umbilical Artery (SUA)

SUA check after birth
Image of normal cord with two arteries.

This is an uncommon finding (about 1 percent of pregnancies and 5 percent of multiple births) but it may be associated with other abnormalities of the fetus. The cut end of the cord should always be inspected after delivery, and if only one artery is seen the child should be carefully examined for any birth defects. If SUA is discovered during a routine prenatal scan, the mother may be offered an amniocentesis to check for signs of chromosome abnormalities like Down syndrome. In some cases the doctor may perform an echocardiogram to test the fetus’ heartbeat.

Umbilical Cord Prolapse
Protrudes into vagina
Cord descends into the vagina before the baby.

Umbilical cord prolapse occurs when the cord protrudes down through the cervix into the vagina before the baby has had a chance to descend into the birth canal. This complication arises in about 1 in every 300 births. The situation can be dangerous because the cord can be squeezed cutting off oxygen supply to the baby. If the baby is not delivered quickly (by cesarean section) it can result in a stillbirth. If your waters rupture and you feel something in your vagina (it is too soon for the baby to be there) go to hospital immediately. The risk of this prolapse is increased if:
• The baby is in a breech position (foot-first).
• You start labor prematurely.
• The umbilical cord is too long.
• There is excess amniotic fluid. This condition is called polyhydramnios.
• Twins are being delivered vaginally, the second baby is more likely to be affected.

Nuchal Cord

wrapped around baby's neck
Umbilical cord wrapped around the neck.

Nuchal cord, as mentioned above is where the cord is wrapped around the baby’s neck (or less commonly other limbs like the arm or foot). It occurs in about 25 percent of deliveries and rarely causes problems. During delivery the treatment for a loop round the neck is to slip it over the head after the baby is born, or if this cannot be done to divide the cord between clamps. If fetal monitoring shows an abnormal heartbeat while the baby is still in the womb, it may reflect that the cord is tightening. The pressure is rarely enough to cause death or long-term problems, but usually a c-section delivery is recommended.

Umbilical Cord Cysts
These are fluid filled cysts (like blisters) that can appear along the cord. True cysts contain early bits of embryo structures and false cysts are fluid filled. Both are associated with birth defects. If they are discovered during a prenatal scan the mother may be referred for genetic testing during pregnancy.

Related Questions
What is cord blood banking? : Consider conserving your child’s umbilical cord for treating potential future health problems.
How is cord blood collected?: Read about the collection process.
How much does cord blood banking cost? :Umbilical cord stem cells.

  Related Articles on Developing Babies

For more information, see the following:

The Female Body: Diagram of a woman's body.
Pregnant with Twins: What to expect when expecting two!

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