Vasa praevia is a condition seen in obstetrics where the foetal vessels run near to or across the internal cervical os.
The foetal vessels are likely to rupture in vasa praevia during rupture of membranes, as the vessels are unsupported by the umbilical cord or placental tissue. This can lead to foetal haemorrhage and foetal death.
Clinical features of vasa praevia (classic triad):
Diagnosis of vasa praevia is usually made with transabdominal or transvaginal ultrasonography and most cases can now be diagnosed antenatally.
Prior to the routine use of ultrasound this condition was usually only diagnosed until after delivery, when haemorrhage has led to foetal death.
Management is with elective caesarean section prior to rupture of membranes. This can be difficult to predict and so is usually arranged at 35-36 weeks gestation. If the mother does however rupture her membranes or go into labour then emergency caesarean section should be carried out immediately.