In the acardia twin scenario, the twin that supplies blood to the acardiac twin is known as the?

• A. Pump twin
• B. Acardia twin
• C. Recipient twin
• D. Donor twin

Answer: (A)

In acardia twin (TRAP sequence) pregnancies, one fetus has a functioning heart and serves as the blood source for the other. Blood from this heart is sent through placental connections into the acardiac twin, which lacks a functional heart and cannot sustain itself. Because that twin is doing the pumping for both fetuses, it is called the pump twin. The acardiac twin receives the deoxygenated blood and often develops with anomalies, while the pump twin bears the extra workload, which can lead to high cardiac strain or heart failure. Recognizing this helps explain why management aims to protect the pump twin by reducing its workload when possible.