The recognition and significance of the vanishing twin.

With the advent of sonography, a twin pregnancy may be diagnosed in early gestation. Serial sonographic examinations can show the disappearance of one of two twins. We offer evidence of an early twin pregnancy with a "vanishing twin," resulting in a liveborn singleton plus a fetus papyraceus. There is an increasing body of information about explanations, management, and complications associated with a multiple gestation and fetal death. The distinction between monochorionic and dichorionic twins is important in their management and for both maternal and fetal prognosis. Identification of dizygotic twins through chromosomal or sonographic studies, revealing separate placentas, separate membranes, or different sexes, theoretically allows the physician to predict a favorable outcome for the live twin and the mother.