Complications of monochorionic twins

Monochorionic twins account for approximately 20% of twin pregnancies. They are at significantly increased risk of fetal and neonatal loss and neonatal morbidity than dichorionic twins. This can be attributed to a number of pathological conditions that can arise due to the shared monochorionic placenta, which contains a number of inter-fetal vascular anastomoses. Specific complications which can arise include; Twin-twin Transfusion Syndrome, Twin Reversed Arterial Perfusion syndrome, single intrauterine death and the complications arising from this for the surviving twin. Monochorionic twin pregnancies may also be complicated by pathological conditions arising from increasingly late embryological division such as monoamniotic monochorionic twins and conjoint twins. These complicated pregnancies are discussed in this review and the obstetric management of these pregnancies is outlined.