Fetal Doppler velocimetry in monochorionic pregnancy: twin reversed arterial perfusion, twin-to-twin transfusion syndrome, and twin anemia polycythemia

The identification and management of complex monochorionic (MC) pregnancy has become reliant on accurate Doppler assessment of both fetal and placental circulations. Twin-to-twin transfusion syndrome (TTTS), twin reversed arterial perfusion (TRAP) sequence, and twin anemia polycythemia sequence (TAPS) are all staged and classified according to fetal pulsed wave Doppler findings, particularly of the ductus venosus (DV), umbilical arteries, and middle cerebral arteries (MCAs). Furthermore, color and pulsed wave Doppler can help delineate the abnormal vascular connections in the placenta and the type of anastomosis whether venous-venous, arterio-venous, or arterio-arterial. These findings are useful in planning management, providing prognostic information and facilitating assessment as to the success of invasive treatment.