Vasa praevia

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

Vasa previa can be of two types

Higher incidence with multiple gestations.

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

The diagnosis is often made with transabdominal colour Doppler sonography demonstrating flow within vessels which are seen overlying the internal cervical os. Occasionally a transvaginal scan is required to better visualize aberrant vessels. Non-Doppler (greyscale) 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

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

On antenatal ultrasound consider

Ultrasound - obstetric
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Article information

rID: 13131
System: Obstetrics
Synonyms or Alternate Spellings:
  • Vasa previa

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