nuchal cord

DEFINITION: Nuchal cord is one or more loops of umbilical cord encircling the fetal neck. It is the most common cord entanglement. Incidence is about 20–34% at term. Single loops are most common (~20–25%), double ~2.5–5%, and triple or more are rare. Incidence increases with gestational age.

RISK FACTORS: Long umbilical cord, polyhydramnios, multiparity, male fetus, excessive fetal movement, small fetus, and monochorionic-monoamniotic twins (cord entanglement in general).

PATHOPHYSIOLOGY: Cord compression, especially during contractions and descent, impairs umbilical venous return first (the vein is thin-walled and compressible). This reduces fetal preload and can cause a transient bradycardia. If compression is severe or sustained, arterial flow is also compromised, causing hypoxemia and acidemia. Wharton's jelly normally protects the cord. Most loops are loose and cause no harm. Tight or multiple loops are more likely to be clinically relevant.

CLINICAL FEATURES / DIAGNOSIS: - Often found at delivery, when the cord is felt around the neck. - Prenatal ultrasound with color Doppler shows a vessel loop around the neck ("divot sign" or "W sign" for multiple loops). It is usually an incidental finding and does not need intervention. - Fetal heart rate tracing: variable decelerations (abrupt drop with rapid return, often V- or W-shaped), which are the classic cord compression pattern. Prolonged decelerations or bradycardia can occur in severe cases. - Neonate: may have a low Apgar score, petechiae or facial/neck bruising, or hypovolemia or anemia in rare cases (from clamping before blood is transfused or from cord compression).

MANAGEMENT: - A nuchal cord found prenatally is NOT an indication for cesarean delivery or induction. - At delivery, check for a nuchal cord after the head delivers. If loose, slip it over the head. If too tight, either deliver the body through the loop ("somersault maneuver") or clamp and cut the cord, then deliver promptly. Cutting is preferred in cases of shoulder dystocia. - Variable decelerations are managed with maternal repositioning (left lateral), IV fluids, oxygen, and amnioinfusion (for oligohydramnios). Stop oxytocin if there is a nonreassuring tracing. Proceed to operative or cesarean delivery if the tracing remains nonreassuring.

COMPLICATIONS: Usually none. Rarely it contributes to fetal hypoxia, neonatal encephalopathy, or stillbirth (especially with tight, multiple loops). Cord accidents are an important cause of unexplained stillbirth, but a nuchal cord alone does not prove causation, since it is also common in healthy fetuses.

HIGH-YIELD BOARD POINTS: 1. Most common cord abnormality at birth. It is usually benign. 2. Classic sign = variable decelerations on CTG. 3. Do not do a cesarean just because of a nuchal cord on ultrasound. 4. Distinguish from other cord problems: cord prolapse (emergency; cesarean, elevate the presenting part), vasa previa (painless bleeding after rupture of membranes, fetal bradycardia, sinusoidal pattern; fetal blood loss), velamentous insertion, single umbilical artery (associated with congenital anomalies), and true knots. 5. Early decelerations = head compression (benign); late decelerations = uteroplacental insufficiency; variable decelerations = cord compression.