Congenital absence of the heart: observation of human funiculopagous twinning with insertio funiculi furcata, fusion, forking, and interpositio velamentosa.

An anatomic and radiologic study of a normal and acardius twinning with a single placenta is presented with literature review. The fetus was unusually well-developed with an almost normal skeletal and brain formation, a normal genito-urinary tract, and an absence of liver, spleen, lungs, and pancreas. The heart was absent but the great arteries, single aorta, and veins were present. The placentation is described as funiculopagous with insertio funiculi furcata, fusion, forking and interpositio velamentosa, and the latter may account for the fusion of the two circulations in this instance with the possibility that the heart was never present. The present and other observations of funiculopagous twins with two amniotic sacs suggest that the forked cord twin anomaly may occur earlier than generally recognized.