Fetal Pleural Effusion

Unlike trace pericardial fluid, which can be seen in normal fetuses, any fluid in the pleural space is abnormal.1,2 The incidence of fetal pleural effusion is unknown, but has been estimated to occur in 1 in 15,000 pregnancies in tertiary care centers.2,3,29 The actual incidence of primary fetal hydrothorax may be even higher if one considers that in many cases the condition may remain undiagnosed, it may resolve spontaneously, the fetus may be aborted, or death may occur soon after birth in outlying hospitals before transfer to a tertiary care center.2 Fetal hydrothorax, either unilateral or bilateral, is a pleural effusion that may be primary, due to chylous leak, or secondary, in which the effusions are part of a generalized fluid retention associated with immune or non-immune hydrops.2,4 The management of pleural effusion in the fetus is complicated by the difficulty in distinguishing primary from secondary hydrothorax. Chylothorax is the most common cause of pleural effusion in the newborn. Secondary fetal hydrothorax is far more common in the fetus than in the neonate. Irrespective of the underlying cause, fetal pleural effusions may be potentially responsible of fetal and neonatal death.3,4 This complication occurs as a consequence of pulmonary hypoplasia due to chronic intrathoracic compression, to hydrops developed from mediastinal shift, cardiac compression, and vena caval obstruction, which diminishes venous return to the heart, resulting in a low-cardiac output state5 and to the prematurity as a consequence of an excess of amniotic fluid secondary to the esophagic compression. Infants affected by pleural effusions usually present in the neonatal period with severe, and often fatal , respiratory insufficiency. This is either a direct result of pulmonary compression caused by the effusions, or due to pulmonary hypoplasia secondary to chronic intrathoracic compression.3,29 The overall mortality of neonates with pleural effusion is 25 percent, with a range from 15 percent in infants with isolated hydrothorax to 95 percent in those with gross pleural effusions.6,7,29 More recently, Longaker et al reported that the mortality rate in cases of antenatally diagnosed chylothorax was 53 percent.2 Fetal Pleural Effusion