Vasa praevia

• Vasa praevia is an obstetric condition where foetal blood vessels cross or run near the internal os of the cervix beneath the foetal presenting part, unsupported by the placenta or umbilical cord.
• These vessels are part of the foetal circulation, connecting the placenta to the foetus, and are at risk of rupture when membranes rupture, leading to foetal exsanguination and death if not promptly diagnosed and managed.

• Vasa praevia is rare, occurring in approximately 1 in 2,500 to 5,000 pregnancies.
• The condition is associated with a high risk of foetal mortality if undiagnosed before labour begins.

• In vasa praevia, the foetal blood vessels, unprotected by Wharton’s jelly and the placental tissue, traverse the foetal membranes across the lower segment of the uterus.
• These vessels are vulnerable to rupture when the membranes rupture or are artificially ruptured during labour, leading to rapid foetal haemorrhage and potential death due to foetal exsanguination.

• Velamentous cord insertion (the umbilical cord inserts into the foetal membranes outside the placental margin, then travels within the membranes to the placenta).
• Succenturiate-lobed placenta (a placenta with one or more accessory lobes connected to the main placenta by blood vessels).
• In vitro fertilisation (IVF) pregnancies.
• Multiple gestations.

• Painless vaginal bleeding in the second or third trimester, particularly after membrane rupture.
• Foetal heart rate abnormalities, such as bradycardia, following membrane rupture, indicating foetal distress.

• Prenatal Ultrasound: Colour Doppler ultrasound is the diagnostic modality of choice for detecting vasa praevia, ideally performed in the second trimester or early third trimester.
• Transvaginal Ultrasound with Colour Doppler: Provides high sensitivity in diagnosing vasa praevia by visualising foetal blood vessels crossing the internal cervical os.

Antenatal Management:

• Once diagnosed, the pregnancy is considered high risk.
• Expectant management involves close monitoring and planning for delivery in a controlled setting.
• Corticosteroids may be administered to accelerate foetal lung maturity if early delivery is anticipated.
• Hospitalisation may be recommended for close monitoring if there’s evidence of vasa praevia bleeding or if the pregnancy is approaching term.

Delivery Planning:

• Planned preterm caesarean delivery, typically between 34-37 weeks gestation, before the onset of labour or membrane rupture, to prevent vessel rupture and foetal exsanguination.
• The exact timing of delivery should be individualised based on the presence of bleeding, foetal lung maturity, and other obstetric considerations.

With timely diagnosis and management, the prognosis for foetuses with vasa praevia has significantly improved, with survival rates approaching 97% in cases where prenatal diagnosis is made.

Early and accurate diagnosis through targeted ultrasound examination is crucial for preventing foetal mortality associated with vasa praevia.

• Vasa praevia is a critical yet rare obstetric condition characterised by the presence of foetal blood vessels across the internal cervical os, putting the foetus at risk for life-threatening haemorrhage upon membrane rupture.
• Early detection through colour Doppler ultrasound, careful monitoring, and planned caesarean delivery before labour onset are key to managing this condition and preventing foetal mortality.
• Understanding the risk factors, pathophysiology, clinical presentation, and management strategies for vasa praevia is essential for medical students and healthcare providers involved in prenatal care and obstetrics.