Introduction and Importance: The TRAP sequence or cardiac mass is a serious pathology that occurs in monochorionic twin pregnancies, characterised by the absence of development of cardiac structures with a series of malformations in the transfused fetus, which is never viable, and numerous complications affecting the transfused twin.

Case Presentation: We report a case of TRAP sequence in a presumed pregnancy at 7 months.

Discussion: The TRAP sequence is an exceptional and specific complication of monochorionic twin pregnancies, affecting on average one birth in 35,000 and 1% of monozygotic pregnancies. The differential diagnosis includes in utero fetal death of a twin without anomalies, anencephaly associated with cystic hygroma and placental tumour. Management of the TRAP sequence in complicated twin pregnancies is aimed at the survival and compensation of the transfused fetus.

Conclusion: Analysis of this observation highlights the importance of prenatal diagnosis in the prevention of its consequences.