Vasa praevia

Question 1

Definition

Answer 1

Cause of antepartum haemorrhage ( bleeding > 24 weeks ) which occurs when the foetal blood vessels cross the internal cervical os, these vessels are unprotected by the umbilical cord or placental tissue and exposed = prone to haemorrhage when the amniotic membranes rupture

Question 2

What are the fetal membranes

Answer 2

Surround the amniotic cavity and developing fetus
- Consist of two umbilical arteries and single umbilical vein

Question 3

Physiology

Answer 3

Umbilical cord containing the fetal vessels (umbilical arteries and vein) inserts directly into the placenta. The fetal vessels are always protected, either by the umbilical cord or by the placenta. The umbilical cord contains Wharton’s jelly = layer of soft connective tissue that surrounds the blood vessels in the umbilical cord, offering protection.

Question 4

Pathophysiology

Answer 4

Fetal vessels are exposed, outside the protection of the umbilical cord or the placenta.
- Fetal vessels travel through the chorioamniotic membranes, and pass across the internal cervical os (the inner opening of the cervix).
- These exposed vessels are prone to bleeding, particularly when the membranes are ruptured during labour and at birth. This can lead to dramatic fetal blood loss and death

Question 5

Type 1 vasa pravia

Answer 5

• The fetal vessels are exposied as a velamentous umbilical cord

Question 6

Type 2 vasa praevia

Answer 6

The fetal vessels are exposed as they travel to an accessory placental lobe

Question 7

Risk factors

Answer 7

Low lying placenta
IVF pregnancy
Multiple pregnancy

Question 8

Presentation

Answer 8

Antepartum haemorrhage = with bleeding during the 2nd or 3rd trimester of pregnancy

Question 9

Diagnosis

Answer 9

USS during pregnancy
- ideal scenario to allow a planned section to reduce risk of haemorrhage
- though not reliable - often not possible to diagnose antenatally
- Detected by vaginal examination during labour, when pulsating fetal vessals are seen in the membranes through the dilated cervix
- May be detected during labour when fetal distress and dark-red bleeding occur following rupture of the membranes. V.high fetal mortality, even with emergency c-section.

Question 10

Treatment ASx

Answer 10

RCOG guidelines (2018) recommend:
- Corticosteroids, given from 32 weeks gestation to mature the fetal lungs
- Elective caesarean section, planned for 34 – 36 weeks gestation

Question 11

Treatment antepartum haemorrhage

Answer 11

Emergency c-section is required to deliver the fetus before death occurs.
- After stillbirth or unexplained fetal compromise during delivery, the placenta is examined for evidence of vasa praevia as a possible cause.