Prenatal diagnosis of a human pseudoacardiac anomaly.

A unique case is presented of dichorionic-diamnionic twins, one of which contained a primitive heart arrested at an early stage of development and which resembled in many other respects a classic case of acardia. Lack of vascular anastomoses, the dichorionic nature of the twins, and ultrasonic evidence of independent heart rates suggest that the primary pathogenesis in acardia may be cardiac dysmorphogenesis rather than reversal of vascular flow. Ultrasonography and fetal echocardiography proved useful in delineating many of the features of the amorphous twin before delivery.