Twin Reversed Arterial Perfusion TRAP; monochorionic twin pregnancies, twins share a single placenta

Описание: Twin Reversed Arterial Perfusion (TRAP) Sequence is a rare and serious complication of monochorionic twin pregnancies, where one twin (the acardiac twin) develops without a functional heart and is perfused by the other twin (the pump twin) through abnormal vascular connections2.

🧠 What Happens in TRAP?
The acardiac twin lacks a heart and often other upper body structures.

The pump twin supplies blood to both itself and the acardiac twin via arterio-arterial anastomoses in the placenta.

Blood flows in reverse direction to the acardiac twin—hence the name “reversed arterial perfusion.”

The acardiac twin cannot survive outside the womb, but its growth can threaten the pump twin’s life by overloading its heart3.

📊 Incidence and Risk
Occurs in about 1% of monochorionic twin pregnancies, or 1 in 35,000 pregnancies overall.

Risk of pump twin mortality is up to 30% by 18 weeks gestation without intervention.

Associated complications include polyhydramnios, fetal hydrops, and preterm birth.

🧬 Types of Acardiac Twins
Type Description
Acephalus Most common; lacks head, may have limbs
Anceps Has head and face, but malformed brain
Acormus Only a head, no body
Amorphus No recognizable body parts; just tissue mass
🩺 Diagnosis
Prenatal ultrasound shows a normal twin and a malformed mass with abnormal blood flow.

Doppler imaging confirms reversed perfusion.

Diagnosis can be made as early as 11 weeks gestation.

💉 Management
Expectant monitoring for mild cases

Radiofrequency ablation (RFA) or laser coagulation to stop blood flow to the acardiac twin

Early intervention (14–18 weeks) improves outcomes for the pump twin


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