# TRAP sequence mimicking placenta bipartita: A diagnostic challenge in prenatal imaging: Case report

## TL;DR

This case report describes a rare prenatal condition called TRAP sequence, which was initially mistaken for placenta bipartita and highlights the importance of early ultrasound diagnosis for better outcomes.

## Contribution

The paper presents a unique case of TRAP sequence misdiagnosed as placenta bipartita, emphasizing the need for improved prenatal imaging techniques.

## Key findings

- TRAP sequence was misdiagnosed as placenta bipartita, delaying proper identification of an acardiac twin.
- Prenatal ultrasound and Doppler studies are critical for diagnosing TRAP sequence and guiding early intervention.
- Macroscopic and histologic findings confirmed the acardius amorphus diagnosis post-delivery.

## Abstract

Twin Reversed Arterial Perfusion (TRAP) sequence is a rare complication of monochorionic twin pregnancies, where one twin without a functional heart is perfused retrogradely by the healthy “pump” twin. Early diagnosis by ultrasound and timely intervention, such as laser photocoagulation, can significantly improve the prognosis of the pump twin by reducing the risk of cardiac failure and preterm birth.

A 33-year-old woman at term presented with decreased fetal movements and was diagnosed with intrauterine fetal demise and a placenta bipartita. Cesarean section for suspected chorioamnionitis revealed a stillborn fetus and an acardiac amorphous twin consistent with Twin Reversed Arterial Perfusion (TRAP) sequence.

Twin Reversed Arterial Perfusion (TRAP) sequence is a rare and severe complication of monochorionic twin pregnancies, characterized by reversed perfusion of a nonviable acardiac twin through vascular anastomoses from the pump twin, putting the latter at risk of cardiac failure. Diagnosis relies on prenatal imaging, especially ultrasound and Doppler studies, with fetal echocardiography and MRI aiding in risk assessment and intervention planning. Early fetal therapy techniques such as radiofrequency ablation or laser photocoagulation have significantly improved outcomes, although the optimal timing of intervention remains under discussion.

This case underscores the complexity of TRAP sequence and the critical role of early ultrasound monitoring and intervention in improving outcomes for the pump twin.

•TRAP sequence is a rare complication of monochorionic twin pregnancies, often misdiagnosed due to its atypical presentation.•This case mimicked a placenta bipartita, delaying the recognition of an acardiac twin.•Prenatal ultrasound remains essential in identifying reversed arterial perfusion and guiding early intervention.•Macroscopic and histologic findings confirmed the diagnosis of acardius amorphus.

TRAP sequence is a rare complication of monochorionic twin pregnancies, often misdiagnosed due to its atypical presentation.

This case mimicked a placenta bipartita, delaying the recognition of an acardiac twin.

Prenatal ultrasound remains essential in identifying reversed arterial perfusion and guiding early intervention.

Macroscopic and histologic findings confirmed the diagnosis of acardius amorphus.