What is this article about?
The blood vessels between the fetus and placenta (umbilical vessels) are usually contained in the umbilical cord. However, in vasa praevia, some of these umbilical vessels are instead located outside of the umbilical cord in the membranes surrounding the fetus, near the cervical opening. Following either spontaneous or artificial rupture of the membranes, these delicate vessels may tear, potentially causing fetal exsanguination. Vasa praevia often coexists with a velamentous insertion of the umbilical cord or a low-lying placenta. It is associated with a high perinatal mortality rate of over 60% if not detected before labour