Which umbilical vessel disappears by 4th month?

Ans. is 'c' i.e., Right vein Umbilical Cord* Most umbilical cords are 40-70 cm long* The cord has three vessels: 1 vein and 2 arteries. The right vein disappears by the 4th month(the left is left).* The O2 supply to the fetus is at the rate of 5-8 mL/kg/min and this is achieved with cord blood flow of 165-330 mL/min.