Multiple pregnancy

The dramatic increase in prevalence of multiple pregnancies owing to the widespread introduction of assisted reproductive technologies (ART) presents unique challenges to obstetricians: not only is the normal dynamic of caring for a mother and her fetus expanded, but also therapeutic intervention that benefits one fetus may result in iatrogenic damage to another. Virtually all pregnancy complications are more prevalent in multiple gestations, resulting in increased rates of maternal and perinatal mortality and morbidity, and leading to a disproportionate workload within obstetrics and fetal medicine. Monochorionic twin pregnancies are particularly at risk and require intensive serial ultrasound surveillance throughout gestation to detect fetal pathologies at an early stage and offer effective intervention. With the specific aim of updating the reproductive medicine specialist, this chapter reviews the complications associated with multiple pregnancy and their management, the roles of prenatal screening and diagnostic testing, and the importance of defining chorionicity at an early stage. Anxiety is high in this setting as many women undergoing fertility treatment want early reassurance about their risks of chromosomal and structural abnormalities on the one hand, but on the other are concerned about the miscarriage risk from invasive testing.