OBJECTIVE To determine the etiology, pregnancy complications, and outcome of isolated fetal pleural effusion diagnosed antenatally and to evaluate the benefits of prenatal fetal interventions. METHODS A literature search of MEDLINE was performed for relevant English language publications between 1985-1991. In addition, reference lists of articles were used to identify reported cases of isolated fetal pleural effusion. METHODS Our search uncovered 31 papers published in peer review journals. From these reports, 82 cases met our selection criteria: All fetuses were diagnosed antenatally with pleural effusion and had no other signs of hydrops at initial diagnosis. METHODS The etiology of isolated fetal pleural effusion was unknown in most cases. Possible causes included congenital chylothorax, goiter, lung tumors, and infection. Cardiac defects (4.9%), Down syndrome (4.9%), and polydactyly (1.2%) may be associated with isolated fetal pleural effusion. Perinatal mortality was high (36%) and was related to the development of nonimmune hydrops, prematurity, and pulmonary hypoplasia. Early gestational age at diagnosis of isolated fetal pleural effusion (32 weeks or less) was associated with poor outcome and a neonatal death rate of 55%. In contrast, the neonatal death rate approached 31% as gestational age at diagnosis exceeded 32 weeks. Fifty-four cases were managed conservatively whereas 24 received intrauterine intervention, which included either pleuroamniotic shunt or repeated thoracenteses. Neonatal death rates were 37 and 33%, respectively. CONCLUSIONS Not enough data exist to support either the conservative approach or intrauterine pleural drainage in cases of isolated fetal pleural effusion diagnosed antenatally.