Twin-to-Twin Transfusion Syndrome: Diagnosis and Treatment

Almost all monochorionic twin pregnancies have a shared placental circulation. Twenty-five percent of these have an imbalance of blood flow leading to chronic shunting of blood from one twin to the other. Severe Twin-to-Twin Transfusion Syndrome (TTTS) develops in up to half of these pregnancies. Prenatal diagnosis relies on findings of oligo/anhydramnios with a decompressed bladder in the donor twin and polyhydramnios and full bladder in the recipient twin. Progressive decompensation is manifested as increasing polyhydramnios leading to preterm delivery, measurable changes in umbilical artery and ductus venosus Doppler velocimetry, fetal hydrops and eventually demise. Historically outcomes without treatment have been poor with a perinatal survival around 10% to 20% with a rate of neurological damage of 20-40% in survivors. Traditionally, treatment has involved repeated reduction amniocenteses to delay early delivery due to polyhydramnios. Lasering of communicating placental vessels has emerged as a new treatment option. A recent randomized controlled trial in Europe comparing endoscopic laser surgery with serial amnioreduction demonstrated an increased perinatal survival, higher gestational age at delivery and a better neurological outcome at 6 months of age in those fetuses randomized to treatment by laser. Endoscopic laser surgery for TTTS is currently only offered at select centers and its technique is still evolving and is the subject of a large multicenter NIH sponsored randomized trial in the United States. Research investigating the use of therapeutic ultrasound for non-invasive coagulation of communicating placental vessels may provide new treatment options in the future.