[Experimental study on cause of pulmonary hypoplasia in the rabbit fetus]

To study the role of thoractic compression in the etiology of pulmonary hypoplasia associated with oligohydramnios, we shunted amniotic fluid into the maternal abdominal cavity at day 24 of gestation (canalicular phase) in one group of fetal rabbits. This procedure produced oligohydramnios and newborns undergoing this procedure had a significantly decreased lung/body weight (LW/BW) ratio at reexploration on day 29. To determine the morphometry of fetal rabbit lung growth, we quantitated the size of lung acinus, the number of terminal airspaces generated terminal airspaces and the diameter of the alveoli was significantly decreased in shunted rabbit fetuses. To examine the influence of the timing and duration of oligohydramnios, we shunted at 22, 24, 26 and 28 days of gestation. The LW/BW ratio and the number of terminal airspaces generated significantly decreased in shunted fetuses on days 22 and 24. To inhibit the loss of fetal lung fluid in oligohydramnios, tracheal ligation (TL) and aminotic fluid shunt (AS) was performed at day 24 of gestation. The TL combined with AS group had the same LW/BW ratio and the number of terminal airspaces generated as the control. We conclude that oligohydramnios induced lung hypoplasia and the degree of lung hypoplasia depends on the time of onset and duration of oligohydramnios, and that lung hypoplasia associated with oligohydramnios is related to the loss of lung fluid.