subject to various complications, the rarest of which is an acar diac fetus, a complication seen in only 1% of all monochorionic twin pregnancies(4). Although the pathophysiology of an acardiac twin is not well known, it is believed that there are vascular anas tomoses that divert blood from the morphologically normal twin to the acardiac twin, a condition known as twin reversed arte rial perfusion. The acardiac twin almost always presents involu tion of the brain, together with the absence or malformation of other organs (Figure 2). The normal twin can suffer complica tions such as heart failure, polyhydramnios, hydrops fetalis, and growth restriction, as well as being at high risk for fetal death(4–6).
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