Two-Vessel Cord and Other Umbilical Complications

The umbilical cord does more than tether your baby to you inside your belly. Starting early in pregnancy, the umbilical cord delivers nutrients and oxygen, and it filters waste to keep your growing baby healthy. So if your health care provider detects a problem with your baby's umbilical cord during your pregnancy, they will want to monitor it closely.

A two-vessel cord, knots, and cysts are among the umbilical complications that your health care provider will look for during a second-trimester ultrasound (also known as an anatomy scan). Learn about signs and treatments when umbilical cord issues arise.

Two-Vessel Cord

A normal umbilical cord has two arteries and one vein. However, some babies are missing either the left or right artery. They have a single umbilical artery, also known as a two-vessel cord.

About 1% of all babies have a two-vessel cord. Babies who are multiples are at a higher risk.

If your health care provider detects that your baby has a two-vessel cord during a routine ultrasound, they might order a more detailed ultrasound, an amniocentesis test, or an echocardiogram of your baby's heart. About 20% of babies who only have one artery in the umbilical cord will have other problems, including issues with their heart, kidneys, or digestive system.

Noncoiled Umbilical Cord

Typically, umbilical cords are coiled, which helps regulate blood flow between you and your baby. Around 5% of babies have cords that are not coiled or barely coiled.

Babies with the lowest degree of coiling in their umbilical cord are at a higher risk for intrauterine growth restriction (IUGR), preterm labor, and distress during labor and delivery. Your health care provider will monitor your pregnancy more closely.

Umbilical Cord Knots

Usually, babies' umbilical cords grow to 22 to 24 inches in your womb. In up to 1% of pregnancies, these cords create a knot around some part of your baby's body. Babies with extra-long cords, those who are smaller in size, and boys are at higher risk for umbilical cord knots.

Knots rarely cause problems until childbirth, when they can cut off a baby's breathing or circulation. Researchers estimate that knots cause about 5% of stillbirths.

When a nuchal cord is loosely looped or wrapped around your baby's neck, it's known as a nuchal cord. Nuchal cords occur in about 20 to 30% of all pregnancies and rarely cause harm to babies.

Specialists most successfully detect umbilical cord knots with 3-D, 4-D, or Doppler ultrasounds. When your health care provider detects a knot through ultrasound or suspect one during fetal monitoring, they can take extra care during labor and delivery. They may recommend a C-section to help keep your baby safe.

Umbilical Cord Cysts

There are two main types of umbilical cord cysts that your health care provider may detect during a routine ultrasound:

• False cysts: The most common type of umbilical cord cyst, these bumps are composed of Wharton's Jelly, the gelatinous connective tissue surrounding the arteries and vein of a normal umbilical cord.
• True cysts: These cysts contain leftover tissue and other materials from earlier stages of your baby's development.

Most cysts resolve on their own and are harmless to your baby. If your baby has more than one cyst, your health care provider may order additional tests, as multiple cysts are associated with an increased risk of miscarriage and some birth defects.

Vasa Previa

In vasa previa, a blood vessel from the cord is not protected by Wharton's Jelly, and crosses your cervix. This can lead to the tearing of the vessel during birth, dilation, or simply pressure at the end of pregnancy.

Vasa previa is a serious complication but thankfully rare, occurring in only 1 in 1,200 to 1 in 2,500 births. You may have bleeding in the second or third trimesters, or your health care provider will pick it up at a routine ultrasound.

Early diagnosis via ultrasound is key. If your baby has vasa previa, your health care provider may recommend a C-section to protect your baby's blood vessels.

Velamentous Insertion

A velamentous insertion means that your baby's umbilical cord is inserted into the membranes rather than the center of your placenta. Your baby's blood vessels are more vulnerable to rupture with this condition.

Up to 11% of singleton babies and 40% of multiples have a velamentous insertion. The good news is velamentous insertion isn't likely to harm your baby. Your health care provider will likely want to monitor your baby closely as they grow.