Monochorionic twins are monozygotic and result from the cleavage of a single zygote. About 70% of monozygotic twins are monochorionic, whereas 30% are dichorionic, depending on the time span between fertilization and cleavage [1] . Monochorionic gestations have a much higher risk of adverse outcome than their dichorionic counterparts because of vascular anastomoses that connect the two circulations. This shared circulation may lead to some unique complications such as twin-to-twin transfusion syndrome (TTTS), twin anemia-polycythemia sequence (TAPS) and demise or neurological damage of the surviving twin if the co-twin dies during pregnancy. Also, the shared circulation mandates a different management of common problems in multiple gestations, such as growth restriction of one twin or discordant abnormalities, because the well-being of the twins is interrelated [2] .
Monochorionic twins have a single placenta, which is less efficient to nurture 2 fetuses to term. In fact, the monochorionic placenta consists of three parts: two belonging to each twin individually and a third shared part.