[CG] Vasa praevia, diagnosis and management

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Definition

Vasa praevia occurs when the fetal vessels run through the free placenta membranes. As these vessels are unprotected by the placental tissue or Wharton’s jelly in the umbilical cord, they are at high risk of rupture when labour commences or when an ARM is performed.

Type 1 – the vessel is connected to velamentous umbilical cord
Type 2 – the vessel connects the placenta to a succenturiate lobe

Incidence

Vasa Praevia is uncommon in the general population with a prevalence of between 1 in 1200 to 1 in 5000 deliveries.

Diagnosis

Antenatal

There is currently no evidence to support screening all women for vasa praevia at the routine FAS.

However for those at higher risk of vasa praeva, (presence of a succenturiate lobe or low lying placenta), a combination of both TA and TV colour Doppler imaging ultrasonography provides the best diagnostic accuracy and performing this at the time of the routine fetal anomaly scan has a high diagnostic accuracy with low false positive rate. However, further research is required to determine the benefit of this.

All patients with suspected vasa praevia should have this confirmed by a further ultrasound in the third trimester

Intrapartum

Vasa praevia may be diagnosed during early labour during vaginal examination by;

  • Detecting pulsating fetal vessels inside the os
  • The presence of dark red vaginal bleeding and acute fetal compromise after SRM or ARM

Fetal mortality rate after rupture is at least 60% despite urgent Caesarean section.

Management

If Vasa praevia is confirmed in the third trimester, deliver by elective Caesarean section between 34 -36 weeks.

Administer antenatal corticosteroids for fetal lung maturity from 32 weeks due to the increased risk of preterm delivery.

Tailor decisions for prophylactic hospitalisation from 30-32 weeks to individual patients, taking into account risk factors such as multiple pregnancy, antenatal bleeding and threatened preterm labour. Outpatient care has been associated with excellent outcomes in asymptomatic women.

Perform an emergency Caesarean section for patients with known Vasa Praevia at viable gestations with SROM and or labour without delay.

If ruptured Vasa Praevia is suspected do not delay delivery while trying to confirm the diagnosis.

Urgent Caesarean section and neonatal resuscitation, including the use of blood transfusion if required, is essential in the management of ruptured vasa praevia diagnosed during labour.

Send the placenta for pathological examination to confirm the diagnosis. This is particularly important where there has been a still birth or where there has been acute fetal compromise during delivery

Offer a post-natal debrief consultation

Last reviewed: 27 August 2020

Next review: 01 August 2022

Author(s): Mandy Reid

Version: 1

Approved By: Obstetrics Clinical Governance Group