Acardiac twinning or TRAP-sequence is a rare complication of monochorionic twin pregnancy. We present a case in which fetal demise of one fetus of a twin pregnancy had been wrongly diagnosed in the first trimester as a vanishing twin. This resulted in the unexpected occurrence of an acardiac twin in the third trimester, culminating in an acardiac twin with a birth weight higher than that of the normal twin. A review is presented on therapeutic opportunities including ligation of the umbilical

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... rd under ultrasound or fetoscopy. This case report highlights the need for correct and early ultrasonographic diagnosis of chorionicity and detailed ultrasonographic follow-up of twin pregnancies.