Fetal hydrops after in utero tracheal occlusion.

In utero tracheal occlusion accelerates fetal lung growth in experimental animals. Following tracheal occlusion, animals with an intact diaphragm can develop hydrops; presumably the enlarged lungs increase intrathoracic pressure, compress the fetal heart, and occlude venous return. In contrast, in animals with a diaphragmatic hernia, even excessive lung expansion has not led to hydrops because the lung can expand through the diaphragmatic defect into the abdomen. The authors had assumed that the diaphragmatic defect in human fetuses with congenital diaphragmatic hernia would provide a similar "release valve" if excessive lung growth occurred. A recent case proved this assumption wrong. At 26 weeks' gestation, an in utero fetal tracheal occlusion was performed on a human fetus with a diaphragmatic hernia. Over the next 9 days there was rapid lung expansion and overdistention, compression of the fetal heart, and hydrops. These findings mimic those seen in fetuses with congenital high airway obstruction syndrome and has implications for in utero treatment of congenital diaphragmatic hernia.