26. Multiple pregnancy

In this chapter, all relevant aspects of multiple pregnancy are discussed: from conception to postnatal care. The management of multiple pregnancies relies on chorionicity due to the different prevalence of prenatal and perinatal complications. Preterm birth is the most important determinant of adverse perinatal outcomes in twins. The additional increased morbidity and mortality rates in monochorionic twins are related to vascular anastomoses, which can result in Twin-Twin Transfusion Syndrome (TTTS), Twin Anaemia Polycythaemia Sequence (TAPS) and Twin Reversed Arterial Perfusion (TRAP). Knowledge of the underlying mechanisms will help to guide women with multiple pregnancies safely through pregnancy and childbirth. The incidence of twins worldwide is highly associated with ART.