Congenital chyloperitoneum as a cause of isolated fetal ascites. Isolated fetal ascites is an unusual prenatal finding and must be differentiated from immune and nonimmune hydrops. This entity is most commonly associated with gastrointestinal and genitourinary anomalies. Fetal chyloperitoneum, however, should be considered as a possible cause. Pulmonary hypoplasia and abdominal dystocia during attempted vaginal delivery are potential complications. We present a case of isolated fetal ascites due to congenital chyloperitoneum. 