Perinatal pulmonary hyperplasia due to laryngeal atresia.

A premature newborn boy, who died at birth because of cartilaginous laryngeal atresia, showed lung development that was far more advanced than normal for gestational age. The lungs, which were histologically normal, were three times the expected weight and showed a degree of alveolarization appropriate for 3 months' postnatal age. The lungs crowded the chest cavity so that the diaphragm was flattened and immobilized; the massive ascites, documented by ultrasound 5 weeks prior to delivery, appeared to be due to obstructed venous return. Thus, the pulmonary hyperplasia, a new finding in perinatal pathology, caused severe fetal ascites. Subsequently, the hyperplasia led to acute polyhydramnios that, ultrasonographically, was observed to develop 2 weeks prior to delivery. The observation that fetal lungs may be hyperplastic has a bearing on the known relationship between fetal lung growth and retention of lung fluid.