umbilical cord

The umbilical cord develops from the connecting stalk and yolk sac during early embryogenesis, typically reaching 50-60 cm in length by term. It contains three vessels: two umbilical arteries (carrying deoxygenated blood and waste from fetus to placenta) and one umbilical vein (carrying oxygenated, nutrient-rich blood from placenta to fetus). These vessels are embedded in Wharton's jelly, a mucoid connective tissue that protects against compression and torsion. The umbilical vein becomes the ligamentum teres hepatis after birth, while the umbilical arteries become the medial umbilical ligaments. Clinically important associations include: Single umbilical artery (SUA), occurring in ~1% of pregnancies, associated with increased risk of congenital anomalies (renal, cardiac) and warrants further fetal evaluation. Nuchal cord (cord wrapped around fetal neck), common and usually benign but can cause fetal distress if tight. Umbilical cord prolapse, an obstetric emergency where the cord precedes the fetal presenting part, risking cord compression and fetal hypoxia—requires emergent cesarean delivery. Vasa previa, where fetal vessels traverse the membranes near the cervical os, risking fetal hemorrhage upon membrane rupture. True knots, which can form during fetal movement and pose risk of cord compression. Cord length abnormalities—short cords associated with abruption or fetal distress during descent; long cords associated with increased risk of cord prolapse or entanglement. Postnatally, the umbilical cord is clamped and cut, with the remnant (umbilical stump) drying and separating within 1-2 weeks, occasionally serving as a site for infection (omphalitis) or umbilical granuloma formation.