Vasa previa

Vasa previa is a term given when there are abnormal fetal vessels within the amniotic membranes that either cross or run in extreme close proximity to the internal cervical os.

Vasa previa can be of two types

Associations

Other associations include a higher incidence with a multiple gestation.

Antenatal ultrasound

Sonographic features are considered generally specific (~90%) 2.

The diagnosis is often made with trans-abdominal Doppler sonography demonstrating flow within vessels which are seen overlying the internal cervical os. Occasionally a trans-vaginal scan is required to aid better visualisation of aberrant vessels. Non-Doppler (grey scale) images may suggest the diagnosis if there are echogenic parallel or circular lines within the placenta near the cervix.

These vessels are unsupported by Wharton jelly or placental tissue and are at risk of:

  • vascular rupture in event of supporting membrane rupture
    • a vessel rupture can result in a catastrophic fetal haemorrhage and often an emergency Caesarian section is required in this situation
  • direct injury during labour

On antenatal ultraound consider:


Ultrasound - obstetric
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Article Information

rID: 13131
System: Obstetrics
Section: Pathology
Synonyms or Alternate Spellings:
  • Vasa praevia

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