Which fetal structure becomes the ligamentum venosum after birth?

• A. Ductus venosus
• B. Foramen ovale
• C. Ductus arteriosus
• D. Umbilical vein

Answer: (A)

Understanding how fetal shunts are remodeled after birth helps explain why the ligamentum venosum forms. In fetal life, the ductus venosus channels oxygen-rich blood from the umbilical vein directly into the inferior vena cava, bypassing the liver sinusoids. After birth, the loss of placental blood flow, higher systemic oxygen, and falling prostaglandin levels cause this vessel to constrict and close. The closed channel becomes a fibrous cord—the ligamentum venosum—located in the liver’s fissure that runs near the porta hepatis to the IVC.

This remnant specifically traces back to the ductus venosus. Other fetal shunts remodel into different ligaments: the foramen ovale becomes the fossa ovalis, the ductus arteriosus becomes the ligamentum arteriosum, and the umbilical vein becomes the round ligament of the liver (ligamentum teres hepatis).