An unusual case of apical diverticulum complicated by serous pericardial effusion and diagnosed ultrasonographically at 13 weeks of gestation is described. A therapeutic abortion was induced at 14 weeks and the complete post-mortem examination did not show additional malformation. Cardiac diverticulum is a rare malformation that occurs as an isolated defect or as part of a complex midline thoraco-abdominal defect. Only two prenatally diagnosed cases have been previously reported in the literature and none with associated hydropericardium.