Management of Monochorionic Twin Pregnancy

A monochorionic twin pregnancy is one in which both babies are dependent on a single, shared placenta. Around one-third of twin pregnancies in the UK have monochorionic placentas. Monochorionic placentation can also occur in higher-order multiples. There has been a recent increase in all types of multiple pregnancies with the increasing use of assisted reproductive techniques. Monochorionic (MC) and dichorionic (DC) twin pregnancies share increased risks of preterm birth, fetal growth restriction, pre-eclampsia, maternal pregnancy symptoms and postpartum haemorrhage. The particular challenges of monochorionic pregnancies arise from the vascular placental anastomoses that are almost universal and connect the umbilical circulations of both twins: twin–twin transfusion syndrome (TTTS), the consequences to the co-twin of fetal death and the management of discordant malformations. In addition, monochorionic, monoamniotic pregnancies (1% of twin pregnancies) carry a very high risk of cord entanglement.