Two Cases of Twin Reversal Arterial Perfusion Sequence

Abstract

Aim: To describe two cases of late presentation of acardiac twin in monochorionic gestation, which was earlier diagnosed as a vanishing twin in first trimester scans and later on found to be an acardiac twin (TRAP sequelae) on follow-up scans. Background: Monozygotic twinning is complicated by anomalous vascular connections in the placenta resulting in clinical syndromes such as twin-twin transfusion syndrome (TTTS), twin anemia-polycythemia sequence (TAPS), and twin reversed arterial perfusion sequence (TRAPS; acardiac twinning). Twin reversed arterial perfusion sequence is a condition arising due to paradoxical retrograde transfusion by a structurally normal “pump” twin, there is a disruption of organ development in the perfused twin. Case description: Twenty-one-year-old G2A1 who was initially diagnosed with vanishing twin in the 14-week scan, which was later on found to be acardiac twinning at 29 weeks and presented with PPROM. She went into spontaneous labor and there was a dilemma regarding delivering her vaginally or by cesarean section. The second case of primigravida, initially diagnosed as single fetal demise at 12 weeks and found to have TRAP sequelae later on at 31 weeks, was admitted and underwent elective LSCS at 32 weeks on maternal request. Conclusion: This lays down the importance of early diagnosis with dedicated ultrasound and management at tertiary care centers for better perinatal outcomes. Clinical significance: The phenomenon of the “vanishing twin” refers to the occurrence of a single fetal loss in a twin gestation during the first trimester. Such cases seen in the first trimester may be a case of acardiac twins, which might become evident later in a growth scan. Hence, it is important to be alert to the possibility of missing an acardiac twin since it is associated with 50% mortality of the pump twin.