Clinicopathological studies on pulmonary hypoplasia in very low birth weight infants.

Seven VLBW infants with pulmonary hypoplasia (P.H.) were studied retrospectively and their necropsied lungs were analyzed morphologically and histometrically in an attempt to establish the clinical and pathological criteria of P.H. Clinically they had various features as follows; 1) causes with oligohydramnios due to amniotic fluid leakage, 2) bell-shaped chest and/or small lung radiographically, 3) severe respiratory distress immediately after birth, 4) frequent complications with air leaks, lethal within several hours after birth. Pathologically they showed a series of changes; 1) remarkably decreased LW: BW ratios, less than 0.015, 2) decreased number of alveoli per alveolar duct, less than 3 or 4 alveoli/duct compared with 6.5 of normal controls at 28 weeks' gestation, 3) immature duct system and increased interstitium which suggested delay in growth and structural maturation of the lungs. It is suggested that the tendency to develop pulmonary air leaks is not only due to high pressure ventilation but also to histological immaturity of the lungs.