<prompt> Which umbilical vessel disappears by 4th month?Right arteryLeft arteryRight veinLeft vein  <response>: 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 monththe left is left. The O2 supply to the fetus is at the rate of 5-8 mLkgmin and this is achieved with cord blood flow of 165-330 mLmin. 