Umbilical-cord ligation of an acardiac twin by fetoscopy at 19 weeks of gestation

Twin reversed-arterial-perfusion sequence is a serious complication of monozygotic multiple gestations, affecting 1 percent of monozygotic twins, or 1 in 35,000 births¹. It has been hypothesized that in the presence of artery-to-artery and vein-to-vein anastomoses in a monozygotic placenta, blood is perfused by the hemodynamically advantaged twin (“pump” twin) to the other twin (“recipient” twin) by means of retrograde flow². Inadequate perfusion of the recipient twin is responsible for the development of a characteristic and invariably lethal set of anomalies, including acardia and acephalus. Typically, the pump twin is structurally normal, but it is at risk for in.