The immature lung: radiographic appearance, course, and complications.

Thirty-six premature newborn infants of a very low birthweight (1,500 g or less) are described who did not have respiratory distress syndrome (RDS) by clinical criteria or by biochemical analysis of pulmonary effluent phospholipid (surfactant). Such patients seem to be protected against the development of RDS by intrauterine stress, which results in accelerated maturation of the surfactant system. Chest radiographs in these patients show a pattern of fine, diffuse granularity together with mild congestion suggesting excessive lung fluid, without significant air bronchograms, underaeration, or cardiomegaly. The most frequent complications are apnea with bradycardia and/or a significant left-to-right shunt through a patent ductus arteriosus. The serious complications of intraventricular hemorrhage, bronchopulmonary dysplasia, and death are more common in the smaller (1,000 g or less) infants; necrotizing enterocolitis, observed in 25% of patients, was not related to birthweight. The radiographic and clinical presentation of "immature lung" should be distinguished from that of RDS, because the prognosis in this birthweight range is considerably better (83% survival).