Twin-to-Twin Transfusion Syndrome: From Placental Anastomoses to Long-Term Neurodevelopmental Outcome

Twin-to-twin transfusion syndrome (TTTS) is a complication of monochorionic twin pregnancies associated with high perinatal mortality and morbidity. Placental vascular anastomoses, almost invariably present in monochorionic placentas, are the essential anatomical substrate for the development of TTTS. According to recent studies, different pathophysiological mechanisms may play a role. Diagnosis of TTTS is no longer based on neonatal criteria such as birth weight discordance and hemoglobin difference, but on strict prenatal ultrasound criteria. A significant evolution in prenatal care strategies and management options for patients with TTTS has occurred during the last decade. Endoscopical laser ablation of communicating placental vessels is a new treatment modality that has led to an increase in survival rates. In perinatology, a decrease in mortality rates may be associated with an increase in morbidity rates. Follow-up studies in infants with TTTS are shedding more light on the wide range of morbidity associated with TTTS, such as neurological, cardiac and renal sequelae. This review analyzes the possible pathophysiological mechanisms involved, discusses the latest findings in diagnosis, therapy and prognosis, and focuses on neonatal and pediatric morbidity associated with TTTS.