Rare presentation of twin gestation with acardiac parabiotic twin

Acardiac parabiotic twinning, also known as a twin reversed arterial perfusion (TRAP) sequence, is a rare occurrence found only in monozygotic twin fetuses whose vascular systems are connected. The circulation of the acardiac twin is accomplished solely by the heart of the other fetus. Although antenatal diagnosis of the TRAP sequence has been reported by several authors, the pathogenesis remains controversial. This case was incidentally detected during routine antenatal sonographic examination at 29 weeks of gestation.