Twin-to-twin transfusion syndrome

Twin-to-twin transfusion syndrome (TTTS) is a severe and unique complication of monochorionic-diamniotic twin pregnancies. It refers to a series of pathophysiological changes and clinical symptoms caused by one fetus (donor twin) continuously transfusing blood to the other fetus (recipient twin) within the uterus. It typically occurs between 15 and 26 weeks of gestation, and if left untreated, the risk of fetal death is over 90%. Pregnant mothers generally do not have specific symptoms other than those related to pregnancy. However, the clinical manifestations in the fetuses vary greatly depending on their blood volume. For example, if one fetus is the donor twin, its blood volume is significantly reduced, which can lead to oligohydramnios, oliguria, anemia, and intrauterine growth restriction. If the other fetus is the recipient twin, its blood volume is significantly increased, which can lead to polyhydramnios, polyuria, edema, and heart failure.