Abnormal fetal cardiovascular morphology Fetal pericardial effusion 2022-01-22T07:37:48Z An abnormal accumulation of fluid in which the heart is partially or completely surrounded by fluid that is seen in all views and the thickness of the fluid as observed by prenatal ultrasound is above age-dependent norms. Fetal pericardial effusion appears in conditions such as hydrops fetalis, heart structural or rhythm alterations, however, it can also be observed in isolation.