Twin reversed arterial perfusion (TRAP) sequence: an acardiac fetus.

To cite: Martins CF, Santos AV, Miranda M, et al. BMJ Case Rep Published online: [please include Day Month Year] doi:10.1136/ bcr-2014-207688 DESCRIPTION A 32-year-old primigravida referred at 22 weeks with contractions. Ultrasound examination showed a 20 mm cervix and a monochorionic diamniotic pregnancy with one structurally normal fetus with hydramnios and a second twin anencephalic and acardiac (figure 1 and video 1). The patient was admitted with the diagnosis of twin reversed arterial perfusion (TRAP) and submitted to amnioreduction. A normal 46 XX cariotype was obtained. Owing to worsening of hydramnios and after counselling, the patient was sent to Hospital Clinic in Barcelona where a successful cord occlusion and laser ablation of the vascular anastomoses was performed at 25 weeks. Two weeks later, she was readmitted with premature rupture of membranes and delivered by C-section at 28 weeks due to severe oligohydramnios. A normal live fetus weighing 1005 g (figure 2) and a 135 g acardiac acephalus twin were born (figure 3). The autopsy confirmed an acardiac twin with no fetal thoracic organs and absent head, a rudimentary bowel and deformed lower extremities (figures 4 and 5). The survival twin remained in the neonatal care unit due to prematurity-related complications and was discharged at 53 days of life. TRAP is a unique complication of monochorionic twin pregnancy, in which a twin with an absent heart (‘acardiac twin’) is perfused by its co-twin (‘pump twin’) via placental arterial anastomoses.