Early diagnosis of conjoined twins by real-time three-dimensional ultrasound--case report and review of the literature.

In 1:50 000 to 1:100 000 births, conjoined twins occur, caused by incomplete division of the embryonic disc more than 13 days after fertilisation. We present a case of cephalothoracopagus janiceps, a very rare form of conjoined twins, which was diagnosed at 13 weeks of gestation. Three-dimensional and colour Doppler ultrasound enabled precise prenatal visualisation of the fusion of the foetal head and chest up to the umbilicus. We could demonstrate the presence of two foetal hearts connected by an arterio-arterial shunt as well as two pairs of upper and lower extremities. After the clear 3-D presentation of the anomaly, making the poor prognosis visible, the mother decided to have the pregnancy terminated. Autopsy confirmed the prenatal diagnosis.