Vasa praevia

Question 1

Are the risks of these greatest to the mother or the fetus?

• Placenta praevia
• Placental abruption
• Vasa praevia

Answer 1

• Placenta praevia - most dangerous for the mother
• Placental abruption - more dangerous for the fetus than the mother
• Vasa praevia - not dangerous for the mother but nearly always fatal for the baby

Question 2

Define vasa praevia.

Answer 2

Occurs when fetal vessels are present in the membranes over the internal cervical os.

Question 3

What are the 3 types of vasa praevia?

Answer 3

Type 1: membranous vessels associated with a velamentous or marginal umbilical cord insertion

Type 2: membranous vessels connecting the lobes of a bilobed placenta or the placenta and a succenturiate lobe

Type 3: one or more large boomerang vessels that run through the membranes along the margin of the placenta, such as with a resolving placenta previa

Question 4

How common is vasa praevia?

Answer 4

~1 in 2000

But higher in assisted conception i.e. 1 in 200

Question 5

What is the aetiology of vasa praevia?

Answer 5

Vessels either:

1. originate from a velamentous insertion of the umbilical cord OR
2. join an accessory (succenturiate) placental lobe to the main disc of the placenta

With (1) there is lack of protection of these vessels from Wharton’s jelly meaning that the vessels are prone to compression and rupture, especially if close to the cervical os.

Question 6

What are the risk factors for vasa praevia?

Answer 6

• Velamentous cord insertion
• Umbilical cord insertion in the lower third of the uterus at first-trimester ultrasound
• Placenta praevia
• Succenturiate placental lobe or bilobed placenta
• IVF
• Multiple pregnancy

Question 7

How is vasa praevia diagnosed?

Answer 7

Antenatal-

• USS with colour Doppler flow - seen as a linear sonolucent are that passes over internal os or within 2cm of it; in 80% of cases VP is associated with placenta praevia, bilobed or succenturiate and cord insertion will be velamentous or marginal

Postnatal - Suspected when either spontaneous or artificial rupture of membrances is accompanied by painless fresh vaginal bleeding from rupture of fetal vessels and sinusiodal pattern on CTG

Question 8

What are the complications of vasa praevia?

Answer 8

• High perinatal mortality from fetal exsanguination - occurs within minutes
• IUGR
• Fetal asphyxia - due to compression of vessels at later gestation

Question 9

What is the management of vasa praevia intrapartum?

Answer 9

If diagnosed antenatally:

• Monitoring - close fetal surveillance as inpatient or ambulatory at 30-34 weeks.
• Expectant management - reasonable up to 34 weeks gestation, as long as there is no fetal distress
• Elective C-section - at 34-37 weeks gestation; goal is to delivery baby before SROM or onset of labour. This can be done earlier if imminent delivery seems likely e.g. at 32-33 weeks.
• Emergency C-section - if there are any signs of labour, SROM or fetal distress.

If major bleeding after rupture of membrance + fetus still alive –> immediate elective caesarean section

Question 10

What is the management of vasa praevia antenatally?

Answer 10

Growth scans - every 4-6 weeks.

Delivery by 40 weeks gestation - IOL and vaginal delivery or C/S

Question 11

List 4 causes of vaginal bleeding in the third trimester.

Answer 11

Bloody show - bleeding during the end of pregnancy as a woman’s body prepares for labor. It’s a common symptom of late pregnancy and can be accompanied by other signs of labor like cramping, pelvic pressure and contractions.

Placental abruption

Placenta praevia

Vasa praevia

Question 12

List 3 causes of PV bleeding in the second trimester.

Answer 12

• Spontaneous abortion i.e. miscarriage
• Hydatidiform mole
• Placental abruption

Question 13

List 3 causes of PV bleeding in the first trimester.

Answer 13

• Spontaneous abortion i.e. miscarriage
• Ectopic pregnancy
• Hydatidiform mole