EP09.113: Case of disappearing acardiac twin with twin reversed arterial perfusion syndrome

Acardiac twin is a rare complication of monozygotic twin pregnancies. A primigravida lady came for her routine first trimester scan. On ultrasound, it was found that alongside a normal fetus corresponding to 13 weeks 3 days of gestation, an amorphous mass having umbilical vein, fundic bubble, liver and few echogenic bony rib and vertebrae like structures were noted; however, no detectable heart like structure or internal cardiac activity was evident on colour Doppler. There was a single placenta with normal attachments of both the umbilical cords. A provisional diagnosis of monochorionic pregnancy with acardiac twin with twin reversed arterial perfusion (TRAP) was given. On subsequent ultrasound done 1 month later, there was significant reduction in size of acardiac twin with no detectable internal or surface vascularity implying spontaneous demise of the acardiac twin without any intervention. Acardiac twin can be considered as the most severe form of Twin–twin transfusion syndrome where abnormal vascular connections from the normal pump twin feed the amorphous acardiac twin. Antenatal diagnosis of this condition hinges on the gray scale and colour Doppler findings in a monochorionic pregnancy where one of the fetuses is dysmorphic, has no cardiac activity and is being parasitically supplied by its vascular connections with the normal twin. In conclusion, monochorionic pregnancies with acardiac twin having TRAP syndrome need close sonographic fetal surveillance Due to hemodynamic dependence of the acardiac twin on the pump twin, it is crucial to monitor the pump twin for signs of decompensation.