Keywords : acardiac twin, amnion, amnionicity, chorion, chorionic sac, chorionicity, conjoined twins, decidua basalis, decidua capsularis, decidua parietalis, decidua, discordant twins, dizygotic twin, donor twin, double decidual sac sign, EFW, embryo, estimated fetal weight, fetal hydrops, gestational sac, intradecidual sac sign, monozygotic twin, oligohydramnios, PCI, placental cord insertion, polyhydramnios, recipient twin, Society of Radiologists in Ultrasound, SRU, stuck twin, TRAP, TTTS, twin demise, twin peak sign, twin reversed arterial perfusion, twin- twin transfusion syndrome, umbilical cord entanglement, velamentous cord insertion, yolk sac