Ultrasound in multiple pregnancy

The advances in reproductive technologies have changed the demographics of multifetal pregnancies. Ultrasound has become the most essential tool to diagnose multifetal pregnancies and to contribute to the surveillance the mother and the fetus during pregnancy, delivery and the puerperium. In the first trimester, it enables us to diagnose the number of vital or non-vital multiples, chorionicity and amnionicity, the presence or absence of nuchal translucency, early growth discordance, severe malformations, and the origin of spontaneous and induced activities. In the second and third trimester, we can exclude malformations and disturbed growth. In addition, the opportunity to examine the cervix by transvaginal ultrasound should not be missed to detect the risk of spontaneous preterm birth. Ultrasound is essential for grading and treatment of twin-to-twin transfusion syndrome (TTTS), the diagnosis of malformations and growth disturbances. Evidence-based medicine has shown that the outcome of twin pregnancies can be improved by early diagnosis and Doppler velocimetry. Before and during labor, ultrasound is necessary for diagnosing the position of multiples, and in order to decide for the optimal route of delivery and in all phases of delayed interval delivery. Postpartum, it can be helpful for the differential diagnosis of severe hemorrhage.