Twin Reversed Arterial Perfusion (TRAP) syndrome, a rare and severe complication of monochorionic twin pregnancies, involves abnormal blood flow between twins due to an arterial connection through the placenta. In this condition, one twin (the "pump twin") supplies blood to the other twin (the "acardiac twin"), which lacks a functioning heart and other critical organs. The excess embryonic fluid, or polyhydramnios, often observed in TRAP syndrome is primarily due to the acardiac twin's inability to regulate amniotic fluid production. Normally, amniotic fluid levels are balanced by the fetus swallowing the fluid and the kidneys excreting it as urine. However, the acardiac twin usually lacks functional kidneys and a gastrointestinal system, so it cannot swallow or process the fluid. This imbalance leads to an accumulation of amniotic fluid around the pump twin. Additionally, the pump twin's heart has to work harder to circulate blood for both twins, which can lead to high output heart failure. This strain may exacerbate fluid imbalances and contribute to polyhydramnios.