 The ductus arteriosus directs blood away from the pulmonary circulation and toward the systemic circulation during fetal life, then closes after birth. In preterm infants the incidence of spontaneous closure decreases with gestational age. Patent ductus arteriosus PDA increases the risks of bronchopulmonary dysplasia BPD and necrotizing enterocolitis NEC. However, this association may not be a causal relationship. 