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Vasa Praevia

Key points

  • Vasa praevia is a rare condition associated with significant risk to the fetus.
  • Antenatal screening for vasa praevia and the management and timing of delivery for diagnosed cases is variable both nationally and internationally.
  • This study aims to provide reliable incidence and risk estimates and describe different management strategies across the UK.

Surveillance Period

1st December 2014 – 30th November 2015


Vasa Praevia describes the fetal vessels coursing through the fetal membranes (amnion and chorion) over the internal cervical os and below the fetal presenting part, unprotected by placental tissue or the umbilical cord. Vasa praevia carries no major maternal risk, but is associated with significant risk to the fetus. When the fetal membranes rupture, the unprotected fetal vessels are at risk of disruption with consequent fetal haemorrhage. Currently routine screening for vasa praevia is not advised by the RCOG and is not supported by the National Screening Committee.1 This is because there is insufficient information on the natural history of the condition and uncertainty about the best test to diagnose vasa praevia. Additionally there is no agreed management pathway for women with confirmed vasa praevia and for women with some risk factors in the absence of vasa praevia.


To use the UK Obstetric Surveillance System (UKOSS) to determine the incidence and risk factors of vasa praevia in the UK over one year and examine the clinical management of the condition as well as maternal and neonatal outcomes.

Research questions

  • What is the incidence of diagnosed/symptomatic vasa praevia in the UK over one year?
  • What are the risk factors for vasa praevia?
  • How is the pregnancy managed following the diagnosis of vasa praevia?
  • What are the maternal and neonatal outcomes of pregnancies complicated by vasa praevia?

Case definition

A case should meet at least one of the criteria below:

  1. Suspected vasa praevia on antenatal US >18 weeks gestation and confirmed vasa praevia on antenatal US >31 weeks gestation (if not delivered prior to 31 weeks)
  2. Palpation or visualisation of the fetal vessels during labour
  3. Rupture of membranes with bleeding associated with fetal death/exsanguination or severe neonatal anaemia
  4. Antenatal or intrapartum bleeding of fetal origin with pathologic CTG and/or positive Apt test
  5. Vasa praevia documented in medical records as reason for admission and caesarean section

AND at least one of the below:

  • Clinical examination of the placenta confirming intact or ruptured velamentous vessels. These may be a velamentous insertion of the umbilical cord or exposed fetal vessels between placental lobes
  • Confirmation of VP on pathological examination of the placenta
  • Torn umbilical cord or placenta (not able to provide placental examination)


This study is funded by UCLH NIHR Research Capability Fund

Ethics committee approval

This study has been approved by the NRES Committee East Midlands - Derby (study ref: 14/EM/1237)

Lead Investigator

Mr George Attilakos, Consultant in Obstetrics and Fetal Medicine, University College London Hospitals NHS Foundation Trust


1 RCOG Green-Top Guideline No. 27. Placenta praevia, placenta accreta and vasa praevia: diagnosis and management. Third Edition. Published January 2011.

Dowload the Data Collection Form (DCF)

UKOSS Vasa Praevia Form

Updated: Tuesday, 17 January 2023 18:40 (v7)