No Treatment Versus Oral Ibuprofen Treatment for Patent Ductus Arteriosus in Preterm Infants

Inclusion Criteria: 1. gestational age of 30 weeks or less or birth weight of 1250 g or less 2. born in Samsung Medical Center 3. confirmed to have hemodynamically significant patent ductus arteriosus (PDA) during day of life (DOL) 5 to 14 4. Definition of hemodynamically significant PDA: ductal size ≥ 1.5 mm with left-to-right shunt (or bidirectional shunt with dominant left-to-right blood flow) on the initial echocardiography plus at least one of clinical criteria. * Clinical criteria * Respiratory signs, including tachypnea, chest retraction, increased respiratory support, unable to wean respiratory support * Physical signs, including a murmur, hyperdynamic precordium or bounding pulses * Blood pressure problems, including decreased mean or diastolic pressure or increased pulse pressure * Signs of congestive heart failure, including cardiomegaly, hepatomegaly or pulmonary congestion Exclusion Criteria: * Mortality within the first 48 hours of life * Ductal size \< 1.5 mm on the initial echocardiography * Right-to-left shunt or bidirectional shunting with dominant right-to-left shunt through PDA * congenital anomaly * bilateral intraventricular hemorrhage of grade 4 * contraindication of ibuprofen (bleeding diasthesis, platelet count 10,000/mm3 or less, serum creatinine 2.0 mg/dL or greater, necrotizing enterocolitis stage 2 or greater