Twin-twin transfusion syndrome - What we have learned from clinical trials.

Monochorionic twin pregnancies are at increased risk for adverse outcome compared to dichorionic twin pregnancies and singletons. Monochorionic-specific complications include twin-twin transfusion syndrome (TTTS), twin anemia-polycythemia sequence, single intrauterine fetal demise and its consequences on the co-twin, and selective intrauterine growth restriction. Whereas the natural history of monochorionic-specific complications carries a high risk of fetal death or severe neurologic disability, a framework now exists, based on well-designed clinical trials, for optimal treatment of these entities. Fetoscopic selective laser coagulation of anastomotic vessels on the chorionic plate has been clearly demonstrated to improve survival and neurologic outcomes for Quintero stage ≥2 TTTS. However, many challenges remain unsolved, the most important of which is preterm premature rupture of membranes. Further improvement in the outcomes of monochorionic pregnancies will require improvements in the rate of premature delivery, and improved diagnosis and treatment strategies for early and late onset TTTS.