Human pulmonary hypoplasia. Statistical, morphological, morphometric, and biochemical study.

Human pulmonary hypoplasia was studied statistically and pathologically in a large series of autopsy cases. Multiple logistic regression analysis indicated five independent risk factors from 10 statistically significant factors for pulmonary hypoplasia: (1) hydrops fetalis; (2) renal anomalies; (3) hernia, including diaphragmatic hernia and omphalocele; (4) skeletal anomalies; and (5) abnormalities of amniotic fluid, such as oligohydramnios and polyhydramnios. The characteristics of pulmonary hypoplasia for each factor were defined by morphological, morphometric, and biochemical methods. All bronchiolar branching, acinar complexity, and acinar maturation were retarded in hypoplastic lungs with hydrops fetalis, renal anomalies, affected side of diaphragmatic hernia, omphalocele, and skeletal anomalies. Only acinar complexity and maturation were impaired in the lung with oligohydramnios due to prolonged rupture of membranes. The pathogenesis of pulmonary hypoplasias should be considered differently with each associated anomaly and time of impairment. While impairment in early gestational stage before 16 weeks' gestation results in both reduced bronchiolar branching and retarded acinar development, that, at late stage, influences only acinar development.