🩸 Vasa Praevia

Course Overview

Vasa praevia is a rare but life-threatening obstetric condition where fetal blood vessels traverse the fetal membranes across the lower uterine segment and are at risk of rupture, typically at the time of membrane rupture. Because these vessels are unsupported by the placenta or umbilical cord, rupture can result in rapid fetal exsanguination. Early diagnosis and planned delivery are critical to optimize fetal survival.

This module provides a detailed understanding of risk factors, clinical features, diagnosis, and management strategies for vasa praevia.

Learning Objectives

By the end of this module, learners should be able to:

1. Define vasa praevia and understand its pathophysiology.

2. Identify risk factors and predisposing conditions.

3. Recognize the clinical presentation and associated fetal risks.

4. Outline essential diagnostic investigations.

5. Formulate management strategies, including timing and method of delivery.

6. Implement supportive care measures to prevent maternal and fetal complications.

 Description

Vasa praevia occurs when fetal vessels traverse the fetal membranes over the internal cervical os and are only protected by the amnion. These vessels may rupture spontaneously during membrane rupture (spontaneous or artificial), leading to rapid fetal hemorrhage. The condition is rare but carries high perinatal mortality if undiagnosed.

 Risk Factors

Several factors predispose to vasa praevia:

• Previous uterine surgery (e.g., caesarean section or myomectomy).

• Abnormal placental morphology, such as a succenturiate lobe.

• Velamentous cord insertion, where the umbilical cord inserts into the fetal membranes rather than directly into the placenta.

Additional risk factors may include multiple gestation, assisted reproductive techniques, and low-lying placenta.

 Clinical Presentation

Vasa praevia often presents at the time of rupture of membranes:

• Per vaginal bleeding: bright red blood appearing suddenly at rupture of membranes.

• Fetal distress: usually severe and immediate, reflecting acute fetal blood loss.

• Maternal symptoms are often minimal since bleeding is fetal in origin.

Prompt recognition is critical because fetal compromise can occur rapidly.

 Diagnostic Investigations

Diagnosis is primarily clinical suspicion confirmed with investigations:

• Kleihauer-Betke test: identifies fetal red blood cells in maternal circulation.

• Cardiotocography (CTG): may show sinusoidal fetal heart rate patterns, indicating fetal anemia or distress.

• Ultrasound: transvaginal or transabdominal ultrasound can identify velamentous cord insertion and the course of fetal vessels over the cervical os.

Early antenatal diagnosis allows for careful planning and prevention of fetal morbidity or mortality.

 Management Principles

Management depends on the timing of diagnosis and maternal-fetal condition:

A. Antenatal Suspected Vasa Praevia

• Hospitalization for monitoring: close fetal surveillance with regular ultrasounds to monitor vessel position.

• Tocolytics: administered if uterine activity threatens premature rupture.

• Bed rest and activity restriction: avoid sexual intercourse, heavy lifting, and straining during bowel movements (use stool softeners).

• Antenatal corticosteroids: to enhance fetal lung maturity in preparation for preterm delivery.

• Avoid vaginal examinations: these may rupture vessels.

B. At Membrane Rupture or Onset of Labour

• Urgent caesarean section is the definitive management to prevent catastrophic fetal blood loss.

• Neonatal preparation: anticipate aggressive resuscitation and blood transfusion for the neonate if needed.

Early planning and timely intervention are key to preventing perinatal mortality, which can be as high as 50–60% without prenatal diagnosis.

 Complications

• Fetal exsanguination and anemia, potentially leading to intrauterine or perinatal death.

• Prematurity due to early delivery.

• Maternal complications are rare but may include anxiety and increased monitoring requirements.

A multidisciplinary approach including obstetricians, anesthetists, neonatologists, and nursing staff is essential for safe management.

 Key Summary Points

• Vasa praevia involves fetal vessels crossing the cervical os and is at high risk of rupture at membrane rupture.

• Risk factors include velamentous cord insertion, succenturiate lobes, and prior uterine surgery.

• Clinical presentation is often sudden, bright red bleeding at rupture of membranes with fetal distress.

• Diagnosis: Kleihauer-Betke test, CTG, and targeted ultrasound.

• Management is urgent caesarean section, with supportive care and neonatal resuscitation readiness.

• Antenatal suspicion allows for hospitalization, activity restriction, tocolytics, and corticosteroids to improve neonatal outcomes.

Recommended References

• Cunningham FG et al. Williams Obstetrics, 27th Edition.

• American College of Obstetricians and Gynecologists (ACOG). Practice Bulletin No. 183: Postpartum Hemorrhage, 2017.

• NICE Guidelines NG201 (2021): Intrapartum Care: Care of Healthy Women and Their Babies During Childbirth.

• Ministry of Health Zambia. Obstetric Care Protocols.