ObjectiveTo evaluate the perinatal outcome after spontaneous single intrauterine fetal demise (IUFD) in monochorionic twin pregnancies with twin anemia-polycythemia sequence (TAPS).MethodsThis was a retrospective study of all monochorionic twin pregnancies with TAPS that underwent spontaneous single IUFD and were registered in the international TAPS Registry between 2014 and 2023. The primary outcomes were mortality and severe neonatal cerebral injury in the surviving cotwin.ResultsA total of 39 twin pregnancies with TAPS that underwent spontaneous single IUFD were included, of which 77% (30/39) developed TAPS after laser surgery for twin-twin transfusion syndrome and 23% (9/39) developed TAPS spontaneously. Single IUFD occurred mostly in the donor twin (35/39 (90%)). The median gestational age at single IUFD was 23.0 (interquartile range (IQR), 20.7-27.9) weeks. The median gestational age at birth of the surviving cotwin was 34.3 (IQR, 32.2-36.0) weeks. Cotwin death occurred in one (3%) case and was due to extreme prematurity and intrauterine fetal infection. None of the surviving cotwins had severe neonatal cerebral injury, nor did any require rescue intrauterine transfusion.ConclusionsIn twin pregnancy with TAPS, the risk of mortality and severe neonatal cerebral injury in the surviving cotwin after spontaneous single IUFD appears to be low, which is probably owing to reduced perimortem transfusion through minuscule placental anastomoses. (c) 2025 The Author(s). Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.