VASA PRAEVIA (RANZCOG)

Question 1

Type 1 vasa praevia, define:

Answer 1

velamentous insertion of umbilical cord into placenta

Question 2

Type 2 vasa praevia, define:

Answer 2

velamentous fetal vessel connecting the placenta to a succenturiate lobe

Question 3

incidence of vasa praevia?

Answer 3

1 in 2500-5000

Question 4

perinatal mortality of prenatally diagnosed vasa praevia?

Answer 4

3%

Question 5

perinatal mortality of vasa praevia not diagnosed antenatally?

Answer 5

66%

Question 6

neonatal transfusion rates for prenatally diagnosed and undiagnosed vasa praevia?

Answer 6

diagnosed = 3.4%
undiagnosed= 58.5%

also associated with cord pH <7 if not diagnosed.

Question 7

TA USS sensitivity vasa praevia?

Answer 7

53-100%

Question 8

TV USS sensitivity vasa praevia?

Answer 8

sens 10%

specificity 99.8% with doppler

Question 9

factors making vasa praevia diagnosis difficult?

Answer 9

TA:
scarring
obesity
empty bladder

TV:
direction of vessels
late first scan (most accurate 18-24weeks)

Question 10

Percentage of vasa praevia resolving in third trimester?

Answer 10

15%

Question 11

Diagnostic criteria for vasa praevia on USS? (4)

Answer 11

• tubular echolucent structure
• blood flow demonstrated with colour or doppler
• umbilical arterial/venous waveforms
• aberrant vessels located overlying or within 2cm of the internal os, attached to inner perimeter of fetal membranes

Question 12

Incidence of velamentous cord insertion?

Answer 12

1% of singleton pregnancies

Question 13

Risk factors for vasa praevia?

Answer 13

velamentous cord insertion
bilobed or succenturiate placenta (OR 22)
placenta praevia
LLP in second trimester (OR 22)
IVF (OR 7 or 1/200)
multiple pregnancy

Question 14

When is TVUSS indicated due to findings on TA USS in targeted screening for vasa praevia? What does SOGC and RCOG recommend? What is the RANZCOG consensus?

Answer 14

RCOG =  no screening
SOGC= screen if below risk factors
1. low lying, succenturiate or bilobed placenta
2. velamentous cord insertion
3. IVF
4. multiple pregnancy

RANZCOG agrees with SOGC

Question 15

Vasa praevia- At what gestation should elective admission for vasa praevia be recommended?

Answer 15

30 weeks. Give corticosteroids. Admit to appropriate centre with NICU availability. Delivery prior to onset of labour.

Other options: outpatient management, serial TVUSS and FfN. 4% risk of preterm emergency delivery.

Question 16

Mean gestational age at delivery for vasa praevia?

Answer 16

34.9 +/- 2.5 weeks. 28% were emergency LSCS for bleeding, labour and ruptured membranes.
‘delivery at later GA may negate the benefit of prenatal diagnosis’.

RANZCOG recommends elLSCS 34-36 weeks.

Question 17

Clinical presentation suspicious of ruptured vasa praevia?

Answer 17

fresh vaginal bleeding
membrane rupture
acute FHR abnormalities 
- progressive tachy
- prolonged bradycardia
- sinusoidal patttern
- fetal death