Overview
Vasa previa is a placental anomaly characterized by fetal vessels crossing over the cervical os, leading to significant risk of fetal hemorrhage and miscarriage, particularly around the time of cervical dilation during labor or spontaneous rupture of membranes 123.Diagnosis
Key Diagnostic Criteria: Exposed fetal vessels running over or within 2 cm of the internal os 1.
Recommended Tests:
- Ultrasound, particularly transvaginal sonography, for cervical length monitoring and identifying velamentous cord insertions 23.
- Transvaginal scanning is recommended for identification but availability varies 3.
Risk Factors: Awareness of risk factors such as velamentous cord insertion, multiparity, placenta previa, and multiple gestations; however, recognition of all risk factors is inconsistent among practitioners 13.Management
First-Line Treatment:
- Elective cesarean delivery at 36-38 weeks gestation to avoid labor and membrane rupture 3.
Adjunctive Measures:
- Close surveillance of cervical length via transvaginal ultrasound to monitor for rapid shortening, which may necessitate earlier delivery 2.
- Chemical tests like Apt and Loendersloot tests can rapidly identify fetal bleeding but are not routine diagnostic tools 4.Special Populations
Pregnancy Management: Focus on early diagnosis and elective delivery timing to mitigate risks 23.
Comorbidities: No specific management adjustments noted in provided abstracts; general principles apply 13.Key Recommendations
Define and Report Vasa Previa Consistently: Use a standardized definition (e.g., exposed vessels within 2 cm of the internal os) and report risk factors at the 20-week anomaly scan 1 (Evidence: Moderate).
Implement Transvaginal Ultrasound for Diagnosis: Offer transvaginal scanning for identifying vasa previa, especially in high-risk cases 3 (Evidence: Moderate).
Schedule Elective Cesarean Delivery: Plan elective cesarean delivery between 36-38 weeks to prevent labor-related complications 3 (Evidence: Expert opinion).
Monitor Cervical Length: Regularly monitor cervical length to assess risk of preterm delivery and adjust delivery timing accordingly 2 (Evidence: Moderate).References
1 Javid N, Hyett JA, Walker SP, Sullivan EA, Homer CSE. A survey of opinion and practice regarding prenatal diagnosis of vasa previa among obstetricians from Australia and New Zealand. International journal of gynaecology and obstetrics: the official organ of the International Federation of Gynaecology and Obstetrics 2019. link
2 Maymon R, Melcer Y, Tovbin J, Pekar-Zlotin M, Smorgick N, Jauniaux E. The Rate of Cervical Length Shortening in the Management of Vasa Previa. Journal of ultrasound in medicine : official journal of the American Institute of Ultrasound in Medicine 2018. link
3 Ioannou C, Wayne C. Diagnosis and management of vasa previa: a questionnaire survey. Ultrasound in obstetrics & gynecology : the official journal of the International Society of Ultrasound in Obstetrics and Gynecology 2010. link
4 Odunsi K, Bullough CH, Henzel J, Polanska A. Evaluation of chemical tests for fetal bleeding from vasa previa. International journal of gynaecology and obstetrics: the official organ of the International Federation of Gynaecology and Obstetrics 1996. link02746-4)