Keywords: Antenatal diagnosis; Benckiser's hemorrhage; Diagnostic anténatal; Hémorragie de Benckiser; Insertion vélamenteuse du cordon ombilical; Placenta previa; Placenta prævia; Transvaginal Doppler sonography; Vaisseau prævia; Vasa previa; Velamentous umbilical cord insertion; Échographie-Doppler endovaginale.