A nuchal cord describes a common occurrence where the umbilical cord wraps one or more times around the fetus’s neck. While the term may sound alarming, this finding is a frequent variation in fetal presentation. Most nuchal cords are not associated with adverse outcomes and do not require specialized management during pregnancy. Medical providers are highly accustomed to managing this condition during labor and delivery.
Defining the Nuchal Cord and Its Frequency
The finding of an umbilical cord encircling the neck is common, occurring in approximately 20% to 30% of all births. This prevalence increases with advancing gestational age, reaching nearly 30% at full term. The umbilical cord is the fetus’s lifeline, containing two arteries and one vein surrounded by Wharton’s jelly. This protective, gelatinous material cushions the blood vessels, maintaining blood flow even when the cord is loosely looped.
The high occurrence rate suggests that a nuchal cord is often a normal consequence of fetal movement. Most entanglements are loose and do not create significant tension or compression on the vessels. Because the cord is cushioned, the condition rarely compromises the transfer of oxygen and nutrients. Multiple loops, such as a double nuchal cord, are less frequent, occurring in about 2% to 8% of deliveries.
Factors Influencing Cord Wrapping
A nuchal cord primarily develops due to the natural, random movement of the fetus within the amniotic fluid. As the baby shifts position, the cord can inadvertently loop around the neck or other body parts. Anatomical factors increase the likelihood of wrapping, including a longer-than-average umbilical cord. A typical cord length is 50 to 60 centimeters, and a longer cord provides more material for entanglement.
An increased volume of amniotic fluid, known as polyhydramnios, also contributes by giving the fetus more space for vigorous movement. Physicians classify nuchal cords into two types based on loop formation. A Type A nuchal cord is an “unlocked” loop that can easily undo itself and is more common. The less common Type B loop is “locked” because the placental end crosses over the baby’s end, making spontaneous resolution less likely.
Prenatal Monitoring and Management
A nuchal cord is often detected incidentally during a routine prenatal ultrasound, usually with Color Doppler imaging that highlights blood flow. When identified, the standard approach is to reassure the parents, as most cases require no specialized intervention before labor. Monitoring fetal well-being remains the focus of prenatal care, regardless of the cord’s position.
Additional fetal surveillance is typically reserved for situations where the nuchal cord is accompanied by other risk factors, such as a decrease in the baby’s movement or evidence of growth restriction. This monitoring may include a non-stress test (NST), which observes the fetal heart rate’s response to movement. Another tool is a biophysical profile (BPP), which combines an ultrasound assessment of movement, tone, breathing, and amniotic fluid volume with an NST. These tests help ensure that the baby is receiving adequate oxygen and blood flow, with a normal result indicating that the baby is currently well.
Interventions During Labor and Delivery
The presence of a nuchal cord is most often discovered after the baby’s head has been delivered. If the loop is loose, the medical provider will gently slip the cord over the baby’s head or shoulder before the rest of the body emerges. This simple maneuver is successful in most deliveries involving a nuchal cord.
If the cord is tight or wrapped multiple times, making it impossible to slip over the head, the medical team will avoid immediate clamping and cutting if possible. Instead, they may employ a controlled technique known as the somersault maneuver. This procedure involves maintaining the baby’s head close to the mother’s body and guiding the baby to deliver the shoulders and trunk through the cord loop, which helps prevent tension and allows for delayed cord clamping. Immediate clamping and cutting is generally avoided, as it can cause the newborn to experience hypovolemia or a lower blood volume.
The cord can sometimes become compressed during the pushing phase, causing variable decelerations, or temporary drops, in the baby’s heart rate. If these decelerations persist and indicate fetal distress, the care team may expedite delivery using a vacuum or forceps. In rare circumstances where the baby’s heart rate does not recover or the cord is severely compressed, an emergency cesarean section may be necessary.