Fetal brain injury in the pump twin of a TRAP sequence with favorable postnatal outcome: a case report

Background: Prenatal diagnosis of abnormal brain lesions in the pump twin of a twin reversed arterial perfusion (TRAP) sequence is exceptionally rare, with only three cases documented in the literature. In this report, we present a case of prenatally diagnosed brain injury in the pump twin, correlating with defined cerebral territory, along with postnatal cranial ultrasound, developmental and clinical outcomes. Case presentation: A 22-year-old pregnant woman was initially misdiagnosed with a monochorionic diamniotic (MCDA) twin pregnancy complicated by single fetal demise. The viable twin corresponded to 17 weeks of gestation, while the demised twin measured 12 weeks with absent cardiac activity. Serial biweekly transabdominal neurosonography remained unremarkable until 25 weeks, when bilateral ventriculomegaly was detected in the surviving fetus. Maternal TORCH screen and fetal SNP array were unremarkable. The patient was referred to a specialized ultrasonography clinic, where re-evaluation confirmed a diagnosis of TRAP sequence. Transvaginal neurosonography and fetal MRI also revealed brain injury with raised suspicion of cortical malformation in the pump twin. Following multidisciplinary counseling, conservative management was selected. At 32 weeks, the patient delivered spontaneously preterm. The pump twin weighed 1,900 g with reassuring Apgar scores, while the acardiac acephalus twin weighed 20 g and exhibited severe malformations. Placental examination confirmed artery-to-artery and vein-to-vein anastomoses. At three weeks of age, cranial 2D and 3D ultrasounds revealed ongoing gyral development, restored cingulate sulcus, stable bilateral ventriculomegaly and partial regrowth of brain tissue in the affected areas. Now at 18 months, the child demonstrates normal growth and continues to achieve her age-appropriate gross motor and neurological milestones. Conclusion: This case underscores the value of comprehensive prenatal imaging in identifying brain injury in the pump twin of a TRAP sequence, raises awareness of its potential occurrence and highlights the possibility of postnatal neurological resilience, even after significant intrauterine challenges. It also emphasizes the importance of long-term postnatal follow-up, as brain development continues beyond infancy.