Prenatal evaluation of cephalopagus conjoined twins by means of three-dimensional ultrasound at 13 weeks of pregnancy.

Cephalopagus twinning, an extremely rare type of conjoined twins, is characterized by the anterior union of the upper half of the body, with two faces each situated on the opposite side of a conjoined head. The prognosis for cephalopagus twins is extremely poor because surgical separation is not an option. Thus early prenatal diagnosis of cephalopagus twins is important to provide an opportunity for pregnancy termination if desired. However, in many instances, cephalopagus twins are misdiagnosed as a singleton pregnancy because of the extreme degree of fusion which makes accurate demonstration of the abnormalities very difficult. This report presents a case of cephalopagus twins which was confirmed at 13 weeks of gestation using three-dimensional ultrasound.