Umbilicals

The umbilical cords, or umbilicals, are flexible structures that connect a developing fetus to the placenta. They serve as the conduit for exchanges between mother and fetus, delivering oxygen and nutrients while removing fetal wastes. In common clinical and anatomical usage, the term refers to the single cord in a pregnancy; the plural refers to cords in multiple pregnancies or corresponding structures discussed across cases.

Anatomy and basic structure: A typical umbilical cord contains two arteries and one vein, surrounded by a gelatinous substance called Wharton’s jelly that cushions and protects the vessels. The arteries carry deoxygenated blood from the fetus to the placenta, while the vein returns oxygenated blood and nutrients to the fetus. At term, cords are usually about 50-60 cm long and roughly 1-2 cm in diameter, though considerable variation exists.

Development and function: The cord forms early in gestation from the connecting stalk and other fetal membranes, with the placenta functioning as the site of gas and nutrient exchange. The vessels within the cord are arranged and coiled to prevent kinking and to maintain a stable connection between fetus and placenta throughout pregnancy.

Variations and clinical considerations: Cord anatomy can vary. Velamentous or marginal placental insertion, abnormal single umbilical artery, and true knots or nuchal cords can occur and may influence fetal oxygenation or birth outcomes. Some anomalies are detectable by ultrasound, and vigilance is important during pregnancy and delivery to manage potential complications.

Perinatal care: After birth, the umbilical cord is clamped and cut. Delayed cord clamping—allowing a short period before clamping in term infants—can improve iron stores and circulatory transition. Proper management of the cord and its vessels is a routine part of obstetric and neonatal care.