Primary fetal hydrothorax: natural history and management.

Primary fetal hydrothorax presents a wide spectrum of severity ranging from small, harmless effusions, to life-threatening thoracic compression. To define natural history and management, we reviewed 32 cases seen at two large perinatal centers from 1980 to 1987. Spontaneous resolution of the effusions was seen in three fetuses, all of whom survived. Three fetuses were electively terminated. The overall mortality was 53%. In the 24 untreated fetuses, sex and the presence of polyhydramnios did not influence mortality, but hydrops, gestational age less than 35 weeks at delivery, and bilateral effusions were associated with a poor prognosis. Five fetuses underwent in utero decompression. In four, thoracentesis was performed, with rapid reaccumulation of the effusion. All four died from pulmonary insufficiency. In the fifth fetus, a thoracoamniotic shunt permanently decompressed the effusion, with resolution of the hydrops, and delivery of a normal viable infant. We conclude that (1) primary fetal hydrothorax may resolve or progress to hydrops, necessitating close follow-up with ultrasound; (2) pulmonary hypoplasia as a result of undrained large pleural effusions may result in neonatal mortality; (3) the gestational age at both diagnosis and delivery, the development of hydrops, and bilaterality of effusions are important prognostic predictors; and (4) the fetus with large effusions and hydrops has a poor prognosis, and thoracic decompression with a thoracoamniotic shunt may prove life saving.