What—and Why—the Neonatologist Should Know About Twin-To-Twin Transfusion Syndrome

Abstract

Twin-to-twin transfusion syndrome results from unbalanced vascular anastomoses in monochorionic twin gestations. This condition, affecting 2,500 pregnancies each year in the United States, is most commonly identified with ultrasonography on the basis of unequal amniotic fluid volumes in a monochorionic, diamniotic pregnancy. Hemodynamic alterations in the syndrome lead to oligohydramnios, intrauterine growth restriction, and frequently, anemia in the “donor” twin while the “recipient” has polyhydramnios and polycythemia. In severe cases, both twins are at risk of developing hydrops fetalis and death. The Quintero staging system is widely used to characterize the features and severity of the disease in a given pregnancy and to guide decisions regarding therapy. The advent of endoscopic fetoplacental surgery, which affords the possibility of laser photocoagulation of connecting placental vessels and thereby separation of the twins’ circulation, has revolutionized the management of this condition and improved outcomes. The main risk of intervention is preterm premature rupture of membranes and subsequent preterm delivery of the twins. The outcomes for survivors of the syndrome are generally comparable to those of monochorionic, diamniotic twins in general and relate primarily to the degree of prematurity.