Twin reversed arterial perfusion (TRAP) sequence

Martin A. Weber; Neil J. Sebire

doi:10.1017/CBO9780511997778.022

Chapter 12.1 - Twin reversed arterial perfusion (TRAP) sequence

Pathophysiology

from Section 2 - Fetal disease

Published online by Cambridge University Press: 05 February 2013

Martin A. Weber and

Edited by

Anthony Johnson and

Mark D. Kilby: Affiliation:
Department of Fetal Medicine, University of Birmingham
Anthony Johnson: Affiliation:
Baylor College of Medicine, Texas
Dick Oepkes: Affiliation:
Department of Obstetrics, Leiden University Medical Center

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Summary

Introduction

Twin reversed arterial perfusion (TRAP) sequence, acardiac anomaly, and chorioangiopagus parasiticus are synonymous terms referring to a rare complication of monochorionic multiple pregnancy characterized by a lack of a well-formed cardiac structure in one fetus (the acardiac twin, which also has numerous associated developmental abnormalities) which is abnormally perfused by a structurally normal co-twin (the “pump” twin) via a large superficial artery-to-artery placental anastomosis. TRAP sequence is therefore unique to monochorionic twins, since the presence of a placental anastomosis is required, and is a consequence of an underlying abnormality of the twinning process and therefore not encountered in singleton pregnancies. TRAP sequence affects around 1 in 35000–40000 pregnancies, representing around 1% of monochorionic twins [1], although higher incidences have been recorded in some series [2]. The pathophysiological basis and pathology of the condition will be discussed below. In this section, prenatal diagnosis and treatment will only be briefly discussed in relation to our understanding of the pathophysiology of the condition; detailed discussion of treatment options is presented in the subsequent section.

Historical perspective

The condition has various names and the term “acardiac monster” was first described in the sixteenth century. It was associated with twin gestation in the early eighteenth century [3]. Having initially been thought to represent a consequence of maternal exposure to environmental events, such as the guillotine, it was demonstrated in the early 1800s that the underlying abnormality was related to vascular abnormalities, and in particular to a primary abnormality or failure of cardiac development in the affected fetus. In 1850 Meckel suggested that the pathogenetic mechanism may be reversed perfusion due to large vascular anastomoses [3]. It is now well documented that many cases are not truly acardiac, and prenatal ultrasound data (see later section) have also demonstrated in some cases the presence of apparently normal cardiac function in early pregnancy with subsequent development of typical TRAP features.

Keywords

twin reversed arterial perfusion sequence placental vascular channels pregnancy prenatal diagnosis monochorionic twin pregnancy fetal growth acardiac fetus

Type: Chapter
Information: Fetal Therapy
Scientific Basis and Critical Appraisal of Clinical Benefits
, pp. 187 - 192

DOI: https://doi.org/10.1017/CBO9780511997778.022 [Opens in a new window]

Publisher: Cambridge University Press

Print publication year: 2012

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References

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Book contents

Chapter 12.1 - Twin reversed arterial perfusion (TRAP) sequence

Summary

Keywords

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References

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