Prenatal sonographic identification of a small rim of pericardial fluid, measuring less than 2 mm in thickness, is a normal finding. Pericardial fluid 2 mm or greater in thickness may be associated with structural anomalies or hydrops, but its clinical significance in the absence of these associated findings has not been evaluated. We assessed the outcome in fetuses with isolated pericardial effusions of at least 2 mm thick. Our study population included 52 fetuses with effusions ranging from 2 to 7 mm in thickness. We compared rates of preterm delivery, cesarean section, intrauterine growth retardation, perinatal complications, Apgar scores, and length of neonatal hospital stay in these 52 cases to the overall hospital rates and found no statistically significant difference. We conclude that in the absence of other sonographic abnormalities, the finding of a fetal pericardial fluid collection 2 to 7 mm in thickness is not associated with adverse outcome.