Vasa Praevia
RCOG Vasa Praevia: Diagnosis and Management (Green-top Guideline 27b). Last reviewed: Sep 2018.
Definition
Vasa praevia is a condition in which the fetal blood vessels run through the membranes overlying the cervical os, leaving them unprotected by the placental tissue or umbilical cord (Wharton’s jelly).
The fetal vessels are often located near or directly over the cervical os, which makes them highly vulnerable to rupture, particularly when the membranes rupture, either spontaneously or artificially.
Aetiology
Primary risk factors:
- Velamentous cord insertion – most common risk factor
- Placenta praevia or low-lying placenta
- Placental structural anomalies (e.g. bilobed placenta, placenta with accessory lobes)
- Assisted reproductive technologies
- Multiple pregnancies
Clinical Manifestation
Classic presentation: painless vaginal bleeding during labour
- The bleeding typically occurs when the membrane ruptures (spontaneously or artifically)
Other key signs during labour:
- Pulsating fetal vessels (detect via vaginal examination)
- Acute fetal compromise immediately after the membranes rupture
Antenatal bleeding is possible and may suggest vasa praevia. However, it has a very low positive predictive value as bleeding is common in pregnancy, while vasa praevia is rare.
Investigation and Diagnosis
Test of choice: transabdominal and transvaginal colour Doppler imaging
Management
There are 3 main scenarios:
| Scenario | Recommended management |
|---|---|
| Asymptomatic women with confirmed vasa praevia (diagnosed prenatally) | Planned Caesarean delivery between 34 – 36 weeks of gestation |
| Patient with known vasa preavia experiences PROM or goes into spontaneous labour | Emergency Caesarean section |
| Vasa praevia unexpectedly diagnosed during active labour |