A new surgery first performed in 1939 by Robert Gross corrected a common pediatric heart problem: patent ductus arteriosus. The ductus arteriosus is a small blood vessel connecting the pulmonary artery to the aorta of a foetus. Since the foetus obtains oxygen via the mother's placenta and not via its own lungs, which are fluid-filled and not yet functional, this vessel provides a shortcut, bypassing the lungs and allowing more efficient delivery of oxygenated blood around the foetus' body. In most infants, the ductus arteriosus closes within a few weeks of birth so that blood flows to the lungs to be oxygenated; if it remains open or 'patent', the normal flow of blood is disrupted. This new surgical procedure artificially closed the blood vessel.