Diagnosis of twin reversed arterial perfusion sequence in the first trimester by transvaginal color Doppler ultrasound.

A case of twin reversed arterial perfusion (TRAP) sequence was diagnosed at 12 weeks' gestation using transvaginal color Doppler ultrasound, which demonstrated the presence of retrograde perfusion in the umbilical artery of the abnormal twin. Ultrasound imaging showed a monochorionic-diamniotic twin pregnancy with an inappropriately grown second twin, the morphological evaluation of which revealed an abnormal cephalic pole with acrania, diffuse subcutaneous edema and the presence of cardiac activity in an abnormal heart with a single chamber.