Twin Reversed Arterial Perfusion (TRAP): A Case Report

Abstract

Background: Twin reversed arterial perfusion (TRAP) sequence is a rare and severe complication of monochorionic twin pregnancies. It represents the most extreme form of twin-to-twin transfusion syndrome and is characterized by retrograde arterial perfusion of an acardiac twin by a structurally normal “pump” twin. This abnormal vascular arrangement places the pump twin at significant risk of cardiac failure and perinatal mortality. We report a rare case of acardiac acephalic twin managed expectantly in a resource-limited setting.

Materials and Methods: This is a case report of a 28-year-old primigravida who presented at 25 weeks’ gestation with suspected fetal malformation. Clinical evaluation, laboratory investigations, and serial ultrasonography with amniotic fluid index (AFI) and estimated fetal weight (EFW) measurements were performed. A diagnosis of monochorionic twin gestation with one normal fetus and an acardiac acephalic twin was made. Due to unavailability of fetal interventional therapy, conservative management with close maternal and fetal monitoring was adopted.

Results: Serial ultrasonography showed stable growth of the pump twin with gradually declining AFI. The patient remained clinically stable until spontaneous rupture of membranes at 30 weeks + 3 days, necessitating emergency caesarean section. A live female neonate weighing 800 g was delivered with good Apgar scores, alongside an acardiac acephalic twin weighing 3.0 kg. The pump twin survived the immediate neonatal period.

Conclusion and Recommendations

Expectant management of TRAP sequence may result in favorable outcomes when the acardiac twin constitutes a relatively small proportion of the pump twin’s weight and there are no signs of cardiac failure. Early diagnosis, serial ultrasound surveillance, and timely delivery are essential, particularly in settings where fetal intervention is unavailable. This study aims to highlight the rare condition and how it presents on the ultrasound.