Monochorionic (MC) twins share a single placenta in utero, rendering them vulnerable to specific perinatal complications that may also significantly affect their lifelong health. Firstly, the vascular connections on the surface of the shared placenta allow for intertwin transfusion during pregnancy. If the transfusion is unbalanced, one twin (the “donor”) gives more blood to the other twin (the “recipient”). When this unbalanced transfusion arises quickly due to the presence of large anastomoses, twin-twin transfusion syndrome (TTTS) occurs. When the unbalanced transfusion is slower due to the presence of only miniscule anastomoses, twin anemia polycythemia sequence (TAPS) may be diagnosed. Secondly, the placental sharing affects the amount of nutrients and oxygen that both twins receive and thereby their growth patterns in utero. When the placenta is unequally shared, this results in selective fetal growth restriction (sFGR), as one twin becomes growth-restricted, while the other twin grows normally. Lastly, if the twins also share a single amniotic sac due to a relatively late split in the fertilized egg cell, these twins are considered monoamniotic (MA). This chapter will touch upon each of these MC twin-specific complications and what there is to know about their postnatal management and long-term neurodevelopmental outcome.