About one third of twin pregnancies are resulting from a single fertilized oocyte. Two third of these monozygotic twins share a common placenta and are therefore called monochorionic. Due to placental sharing and the ever-present inter-fetal vascular connections, specific complications may arise and lead to an increased risk of intrauterine death and long-term neurodevelopmental impairment. Specific complications include twin-to-twin transfusion syndrome (TTTS), twin-anemia-polycythemia sequence (TAPS), selective intrauterine growth restriction (sIUGR) and discordant major anomalies, occurring in about 10%, 5%, 20% and 6% of monochorionic diamniotic twins. Prenatal interventions may improve perinatal and long-term outcome of affected fetuses. However, general knowledge about early diagnosis of monochorionic twins and their specific complications is still limited in a significant number of practitioners in Austria and systematic analysis of pregnancy outcomes are not conducted.