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Vasa Praevia: A preventable tragedy Elizabeth Daly-Jones Ultrasound Services Manager Queen Charlotte’s and Chelsea Hospital, London


Outline • What is Vasa Praevia (VP)? - Incidence - Implications • Diagnosis with ultrasound - Assessment of cord insertion site - Assessment of placental appearance / location - Consideration of other risk factors • Difficulties in diagnosis • Best practice guidance • Conclusions


What is Vasa Praevia (VP) • A life-threatening condition linked to fetal / neonatal death • Fetal vessels course over or close to cervix beneath the presenting part - Unprotected by Wharton’s jelly or placental tissue

• The vessels are vulnerable to laceration and compression - Most commonly at the time of delivery


Classification of Vasa Praevia • Type 1

• Type 2

Velamentous cord insertion (VCI)

Vessels join placenta to accessory lobes


Incidence • Approximately 1 in 2,500 deliveries • Of 734,000 UK births last year 293 would be affected • Also note the incidence in IVF pregnancies may be 1 in 300 • Note the true incidence is likely to be higher than reported figures


Incidence (Cont.) • The reporting of Vasa Praevia underestimates the scale of the problem • Death certificates in England and Wales which mention vasa praevia have the following incidence - 2001: 1 - 2002: 0 - 2003: 2 - 2004: 1 - 2005: 0 • QCCH interim audit results suggest 1:1250


Implications • Fetal or neonatal death due to exsanguination or asphyxiation • Antenatal diagnosis via ultrasound and caesarian section are critical to reduce high mortality rate - e.g. a multi-centre trial of 155 cases of VP found those with a pre-natal ultrasound diagnosis had a 97% survival rate compared with 44% without


Diagnosis with ultrasound • Assessment of placental cord insertion site • Assessment of placental appearance and location • Consideration of risk factors


Assessment of cord insertion site • In 1% of pregnancies cord inserts away from placental edge - VCI leads to a higher risk of Vasa Praevia (6%) • Use high resolution grey-scale ultrasound to image the fetal surface of the placenta • Use colour flow imaging to distinguish entry of umbilical vessels from loops of umbilical cord • Evaluate the internal os area with TA or TV scan and crucially with colour doppler


Assessment of cord insertion site

TA grey-scale image of insertion site

TA using colour doppler


Assessment of cord insertion site

TV of a VP Type 1

TV with colour doppler


Assessment of cord insertion site

TV doppler image

Pathological specimen of a VCI


Assessment of placental appearance / location • Fetal vessels crossing the cervix between placental lobes typical of VP type 2 • Placenta praevia and low lying placenta represent additional risk factors • Assessment of the placental site in relation to the internal os • Utilise colour doppler over the area around the cervix • Transvaginal scan if optimal visualisation is elusive


Assessment of placental appearance / location

VP type 2 - vessels crossing cervix between the main lobe and the succenturate lobe

Bilobed placenta with VCI


Consideration of other risk factors Succenturate Multi-lobate placenta IVF pregnancies

Low lying placenta or placenta praevia

(1:300)

Risk Factors PV Bleeding

Multiple Pregnancies Velamentous insertion (6% associated with VP)

(10% of VP occurs in twins)


Difficulties in diagnosis • Factors that make assessment of VP difficult - Obesity - Abdominal scarring - Awkward fetal position - Flash artefacts


Difficulties in diagnosis • Beneficial strategies - Colour flow mapping to assess cord insertion

- Visualisation during 2nd trimester given greater fluid volume - Abdominal manipulation and lateral positioning of mother - Transvaginal examination of lower segment


Difficulties in diagnosis

Transabdominal scan showing cord close to internal os

Use of Doppler to confirm a suspicious structure is not a vessel


Difficulties in diagnosis

TA scan with possibility of vessels near cervix

Repeat image confirming flash artefact


Best practice guidance • The exclusion of vasa praevia during the anomaly scan should be standard practice • Departmental protocols should reflect this • Tools, such as the Astraia fetal database, can offer support - Mandatory fields can and should be created


Best practice guidance • The UK Vasa Praevia Awareness Group offer training material (see www.vasapraevia.co.uk for more details) • Jeanty’s algorithm for the 2nd trimester anomaly scan also provides valuable guidance


Best practice guidance


Conclusions • Evaluation to exclude VP should be adopted in all routine anomaly scans as a matter of urgency • Until this occurs babies will die unnecessarily and families will continue to suffer the avoidable loss of a healthy baby


Thank you!


Contact details Elizabeth Daly-Jones Ultrasound Department Queen Charlotte’s and Chelsea Hospital Du Cane Road London, W12 0HS elizabeth.dalyjones@imperial.nhs.uk


Vasa Previa talk Oct 08 V2