patent ductus arteriosus: a ductus arteriosus that failed to close at birth; may require surgical correction
ductus arteriosus: a blood vessel in a fetus that bypasses pulmonary circulation by connecting the pulmonary artery directly to the ascending aorta; normally closes at birth
national insurance: social insurance program in Britain; based on contributions from employers and employees; provides payments to unemployed and sick and retired people as well as medical services