This study is aimed to evaluating the understanding of antenatal screening for Down syndrome by pregnant women. To assess the level of understanding, a prospective and monocentric study was conducted in a single health centre, the University Hospital of Caen using questionnaires, filled in by patients attending obstetric consultation, whatever the stage of their pregnancy. Although this test is offered to all patients, information to be delivered by health professionals is not clearly understood by a number of patients. Explanations need to be improved and one must also ensure that they are fully understood.