Separation of Conjoined Twins with the Twin Reversed-Arterial-Perfusion Sequence after Prenatal Planning with Three-Dimensional Modeling

There are two congenital anomalies specific to multifetal pregnancies: twin reversed-arterial-perfusion sequence and conjoined twinning. The twin reversed-arterial-perfusion sequence is a rare complication of monozygous twinning in which one fetus (the “pump” twin) perfuses the other fetus (the “perfused” twin), resulting in reversed flow in the umbilical vessels and multiple structural anomalies, including acardia, in the perfused twin.1 It occurs in fewer than 1 percent of pregnancies with monozygous twins and in about 1 in 35,000 births overall.2,3 Conjoined twinning occurs as a result of incomplete duplication of a single blastocyst during the process of monozygotic twinning.4 It is . . .