Characteristic pattern of Doppler umbilical arterial velocity waveform in conjoint twins

Doppler blood flow studies in a pair of conjoint twins at 18 weeks gestation revealed a characteristic 'double layer' spectral velocity waveform from the umbilical arteries. This is the result of signals originating from 2 separate arterial supplies adjacent to each other in a single umbilical cord. Such a characteristic feature provides an additional sonographic sign in the diagnosis of conjoint twins.