In most cases, the umbilical cord is about 20 inches long and almost one inch in diameter. It usually appears loosely coiled. Inside the cord are two arteries and one vein—the vein supplies the baby with oxygenated, nutrient-rich blood, and the arteries carry de-oxygenated, nutrient-depleted blood back to the placenta. On occasion, the umbilical cord will only have two vessels—one artery and one vein.

Depending on the nature of the knot, nuchal cords are classified into two types:

• Type A Nuchal Cord: When the umbilical cord wraps around a baby’s neck 360 degrees, it is called a nuchal cord, or type A nuchal cord.
• Type B Nuchal Cord: A type B nuchal cord pattern occurs when the cord cannot be undone and ends up as a true knot.

Nuchal cords are very common, with prevalence rates of 15 to 34 percent at term. A nuchal cord may form at any time. Nuchal cords may form, disentangle and reform, or they may persist. In some cases, a nuchal cord may not affect pregnancy outcome significantly. In others, the nuchal cord may lead to restricted fetal blood flow (ischemia), decreased oxygen (hypoxia), decreased fetal development, diminished fetal movement and complicated delivery. All of these complications significantly increase a baby’s risk for birth asphyxia. Mechanisms that cause ischemia and hypoxia / asphyxia include:

• Restriction of carotid artery (neck artery) blood flow from tight nuchal cord entanglement around the neck
• Severe congestion of venous blood flow
• Compression of the umbilical cord vessels themselves when the nuchal cord becomes tightly compressed against itself or the baby’s neck

Nuchal cords are often identified during an obstetrical ultrasound. To identify a nuchal cord, physicians look at multiple views of the fetal neck. A nuchal cord is diagnosed when the umbilical cord is seen encircling at least three-quarters of the fetal neck. If the cord encircles at least half of the neck, it may be classified as suspicious for the presence of a nuchal cord. The sensitivity of ultrasound for detecting nuchal cords at term has been reported to be about 70% for gray-scale imaging, and 83% – 97% with color Doppler.

The main goal in managing a nuchal cord is to prevent umbilical cord compression during delivery. Preserving an intact nuchal cord will depend on how tightly it is wrapped around the baby’s neck. A loose nuchal cord can usually be easily slipped over the baby’s head to decrease traction during delivery of the shoulders or body. If this is not possible due to tightness, there is a technique wherein the physician may be able to slip the cord over the infant’s shoulders. If this is also not possible, the physician may use the somersault technique, which allows the shoulders and body to be born in a somersault, with the cord being unwrapped after the baby is delivered.

Sometimes, if there is more than one loop or the loop is too tight and cannot be removed easily, the cord must be clamped and cut before the delivery of the shoulders to ensure adequate oxygen supply to the baby.

If a vaginal delivery is prolonged and threatens the health, safety or life of the baby, an emergency C-section must be performed. A delay in performing a C-section can severely exacerbate the detrimental effects of hypoxia and ischemia, and can lead to serious brain injury.

The physician and medical team must be very knowledgeable and skilled at handling issues that arise during labor and delivery that can deprive the baby of blood and oxygen. The team must be able to act quickly. Failure to properly monitor and treat the mother and baby during pregnancy, labor and delivery is medical negligence. Failure to follow standards of care and guidelines, and to act skillfully and quickly, also constitutes negligence. If this negligence leads to injury of the baby, it is medical negligence.