Spontaneous improvement of intrathoracic masses diagnosed in utero.

The diagnosis and pregnancy outcome for 14 fetuses with sonographically detected chest masses were reviewed retrospectively. Six lesions became smaller or less apparent during gestation or resolved between antenatal and perinatal imaging studies; these included all three types of cystic adenomatoid malformation (CAM), as well as one case of pulmonary sequestration (PS). This information is extremely important in counseling patients in the second trimester who are considering termination of pregnancy. The poor prognosis traditionally assigned to type II and type III CAM needs changing to reflect the phenomenon of improvement with excellent long-term outcomes. Sonographic indicators of poor outcome were polyhydramnios, hydrops or marked cardiac deviation.