[Vasa previa: one case].

Vasa previa is a rare condition (1/2000 to 1/5000) in which the rupture of membranes may result in fetal haemorrhage (Benckiser's haemorrhage). We report one unusual case of delayed Benckiser's haemorrhage 12 hours after rupture of membranes. We point out the risk situations in which prenatal diagnosis should particularly be sought: low-lying placenta at routine second trimester ultrasound screening, bilobate or succenturiate placenta, velamentous insertion of the umbilical cord, in vitro fertilization. A universal screening, as proposed by certain authors, is also discussed.