[Diagnosis and surveillance of multiple pregnancies by echography]

Twin pregnancies are high-risk pregnancies requiring a particularly close supervision in which ultrasonography plays a major role from the beginning to the end. At the beginning, ultrasonography shows the presence of a twin pregnancy and provides an indication of its anatomical type. It may also detect early complications, notably lysis of the ovum. From the second trimester of pregnancy onwards, ultrasounds diagnose complications that are not readily accessible to physical examination, such as growth retardation of one foetus or both, foetal malformations or death in utero of one of the twins. At the end of pregnancy, ultrasounds also plays a role in the choice of the mode of delivery.