Twin pregnancy: the role of ultrasound in management

Determination of chorionicity is one of the most important issues in the ma nagement of twin pregnancy. Modern ultrasound equipment has made it possible to accurately assess place ntation already in the first trimester with the lambda sign. With regard to l prenatal diagnosis, it is important to know the chorionicity in order to calculate the risk of chromosomally abnormal fetuses. Accurate chorionicity offers the obstetricians the opportunity to observe the monochorionic twin s more intensively than is required for twins with dichorionic placentation . This review gives an update of the state of the art for clinicians caring for twin pregnancies.