ABSTRACT
The ductus arteriosus of many preterm infants remains patent at birth. Patency approaches 90 percent under 28 weeks’ gestation, 75 percent at 28-31 weeks, 45 percent at 31-33 weeks, and 21 percent at 34-36 weeks. When correlated with weight, there is 83 percent patency under 1000 g; this falls to 47 percent in those weighing 10001500 g at birth and 27 percent in neonates weighing more than 1500 g. While spontaneous closure is directly related to arterial oxygen tension, there are many additional factors that affect functional and anatomic closure, and reopening, in both the premature and full-term infant.
