What Does the Umbilical Cord Do?
The umbilical cord carries life-giving blood to a baby while it grows inside the mother’s womb. The cord attaches from the baby’s stomach to the placenta, a disc-shaped organ in the mother’s uterus wall.
Cords come in different lengths and thicknesses, but their structure is the same: inside, two arteries bring blood containing oxygen and nutrients to the baby; one vein takes away waste products, de-oxygenated blood, and carbon dioxide; and these three blood vessels are cushioned by a gelatinous substance called Wharton’s jelly, which is all wrapped up in a membrane called the amnion.
The umbilical cord is the lifeline from mother to baby for the entire nine months of pregnancy and well into the birthing process. Sometimes, complications arise inside or outside of the cord.
Risk Factors for Complications
If anything goes wrong with the umbilical cord, the baby loses some or all access to oxygen, nutrients, and more. These factors may increase your risk of umbilical cord complications, but they can realistically happen to any pregnant mother:
- Twins or multiple births
- Over 35
- Having first baby
- Used assisted reproductive technology (ART)
- Umbilical attachment factors in previous pregnancies
Causes of Umbilical Cord Complications
- Length of the Cord
Umbilical cords can range in size from “no cord” to an impressive 300 centimeters. Normal or average cords are around 50–55 cm. If a cord is too long or too short, certain complications are more likely to occur.
- Long cord
Longer cords can cause fetal entanglement, knots in the umbilical cord (which can cause “compression” or choke off the baby’s supply of oxygen), and thrombi (blood clots). About 5% of umbilical cords are longer than 80 cm.
- Short cord
If an umbilical cord is too short—usually judged at less than 35 cm—the baby might not have enough cord to move around in the uterus, which helps stimulate growth. Of course, the baby’s movement usually lengthens the cord, so which one is truly to blame is not always clear. Short cords occur in 5% of American pregnancies, and can cause delayed development to the baby or tears in the cord, and even keep the baby from being born vaginally. Short cords are often seen alongside other congenital problems, so if detected, doctors should run tests. Short cords double the danger of stillbirth.
- Long cord
- Where the Cord Inserts
Normally, the umbilical cord runs from the baby’s future bellybutton to the center of the placenta. If the insert site is slightly off the center, there’s no danger. But when the cord attaches near the edge or off the placenta entirely, as in around 10% of cases, there is danger to the baby.
- Marginal umbilical cord insertion
Only 7% of pregnancies have what is known as “Battledore cord insertion” or marginal cord insertion. The umbilical cord connects within 2 cm of the placenta’s edge instead of near the center. Usually, this is not a problem—many women with this condition deliver healthy babies. As long as the baby is receiving a good flow of oxygen and nutrients from the mother, there is no need to worry. But marginal cord insertion can develop into the dangerous velamentous cord insertion later in pregnancy, so it must be monitored carefully. Ultrasound should be able to spot this condition.
- Velamentous cord insertion
The cord implants itself next to the placenta, in neighboring tissue, and then travels to the placenta. There is no way to correct velamentous cord insertion, but as long as the baby is still receiving blood from the mother, the pregnancy can be successful, though studies have shown one in four end in miscarriage. This condition is nine times more likely in twin or multiple-birth pregnancies. Can result in premature birth, decrease in fetal development, excessive bleeding during childbirth, fetal distress, and vasa previa.
- Vasa previa
When there are blood vessels in the uterus right in front of the area where the fetus needs to come out at the opening of the cervix, childbirth can rupture them. Vasa previa is a “high-risk” condition that can lead to excessive bleeding, fetal distress, and even stillbirth. C-sections are necessary when fetal distress is apparent. Vasa previa is very important to diagnose and monitor. If untreated, death is likely.
- Marginal umbilical cord insertion
- Problems Inside the Cord
Some underlying factors, like a disease in the mother that causes easy clotting, can make problems inside the umbilical cord more likely. But for most of these complications, medical science isn’t completely sure why they occur, and can only monitor the mother once the danger is known.
- Single umbilical artery (SUA)
A healthy umbilical cord has three blood vessels: two arteries and one vein. Sometimes, one artery never forms. Usually, SUA is only a concern when more complications are present—and it sometimes indicates that other congenital factors are present. 20% of SUA cases have associated anomalies. This complication can be diagnosed prenatally, so if it’s found, medical providers should aggressively test for other problems. SUA is present in 1% of single births and 5% of twin or multiple births.
- Cord hematoma or ulceration
A cord hematoma is when blood leaks out of the umbilical veins or arteries inside the cord. It can be caused by prenatal procedures. Ulceration is more severe—when these vessels rupture and the baby bleeds inside the womb. Currently, this complication is not detectable, but fetal distress should be apparent during the birthing process.
- Cord cysts
Whether a true or false cyst (pseudocyst), this complication is very rare—only found in 0.4% of pregnancies. These cysts are more common at the fetal end of the cord near the baby’s stomach, but they can be any shape and size along the cord. Cysts can be found in the first trimester. Cyst rupture is a danger during labor and C-section delivery is recommended.
- Cord tumors
Umbilical cord tumors, either hemangiomas or teratomas, are extremely rare. They usually form on the placental end of the cord. They cannot be reliably diagnosed before birth; they just appear as a “cord mass” on ultrasound. An alpha-fetoprotein (AFP) test may be done, and if the number is high, there may be tumors.
- Blood clots
Umbilical cord thrombosis is when one of the blood vessels in the cord is blocked by clotted blood. It is most common in the umbilical vein. Since the blood flow to the baby is restricted, thrombosis requires prompt emergency treatment. This condition happens in an estimated one in 300 pregnancies.
- Single umbilical artery (SUA)
- Compression of the Cord
If the umbilical cord is knotted, kinked, or squeezed tightly, even the gelatinous Wharton’s jelly can’t cushion the blood vessels enough to keep up the blood-and-oxygen flow to the baby. The umbilical cord is made to withstand quite a bit of twisting or kinking. The baby is only in danger if the compression doesn’t allow oxygen to reach it for a long enough time.
- Cord knots
There are two types of cord knots: true and false. False knots are minor kinks in the cord. They are fairly common and cause few real problems. True knots are much rarer—in only 1% of pregnancies. When the knot tightens, the baby’s oxygen supply is choked off. A longer umbilical cord, more active baby, and greater amount of amniotic fluid (polyhydramnios) all contribute to a true knot. Luckily, these can be detected by ultrasound.
- Nuchal cord
Nuchal cord is when the umbilical cord is wrapped completely around the baby’s neck. A “double nuchal” is wrapped twice. This is somewhat common (see in more than 20% of pregnancies), and surprisingly, not as dangerous as it looks. As long as the cord isn’t compressed, the baby is still “breathing” through its bellybutton, not the head. A longer cord and induced labor are associated with nuchal cord, which can be detected by color Doppler or ultrasound.
- Cord stricture
A “narrowing” of a section of the umbilical cord, leading to constriction or blockage of the blood flow from mother to baby. The cause of umbilical cord stricture is unknown, and it cannot be diagnosed prenatally. The baby is usually stillborn.
- Cord prolapse
This condition happens during birth when the umbilical cord slips out of the birth canal either before the baby (overt prolapse) or alongside the baby (occult prolapse). Rupture of the amniotic sac can make prolapse more likely. Since the baby is squeezing against the birth canal as well, umbilical cord prolapse almost always causes cord compression and is treated as an obstetric emergency. C-sections are usually required.
- Cord knots
Umbilical cord conditions can increase the risk of birth defects, birth injury, or stillbirths. There are no treatments just yet for most of these complications—medical providers rely on monitoring the problem, and intervening if things look dangerous.
Ultrasonography is becoming more and more sophisticated; many complications can be detected early in pregnancy, even in the first trimester. But in America, there is no standard testing for umbilical cord complications at this time, though more and more are being discovered sooner than in years past. Petitions have been proposed, but the best way of ensuring your baby isn’t at risk is to educate yourself and ask questions. Insist on testing if things don’t seem right.
If you feel that an umbilical cord complication wasn’t diagnosed or dealt with in a timely manner and your baby suffered as a result, you may be right. Speak to Laura Brown at Brown Trial Firm at +1 (866) 393-2611. She can sit down with you and go over your case.
- Medscape: Umbilical Cord Complications
- National Institutes of Health: Length of Umbilical Cord
- DoveMed: Marginal Insertion of the Umbilical Cord
- DoveMed: Short Umbilical Cord
- Radiopaedia: Velamentous Cord Insertion
- AmericanPregnancy.org: Umbilical Cord Prolapse