Vasa previa is defined as fetal vessels that run through the fetal membranes, over or near the endocervical os (2 cm or less) and are unprotected by placenta or umbilical cord.

CLINICAL ACTIONS:

Deliver by cesarean section before the onset of labor and before rupture of membranes

• Scheduled delivery 34w0d to 37w0d
• Deliver by cesarean section in the case of PPROM and viability
• Antenatal corticosteroids 28 to 32 weeks gestation
• SMFM guidance states to consider hospitalization at 30 to 34 weeks
  • Benefit is unproven and there have been good outcomes reported with outpatient management
  • When considering hospitalization, individualize based on the following
    • Symptoms
    • History of preterm birth
    • Logistics in getting to hospital with transfusion capabilities
  • Patients with normal cervical lengths are the best candidates for possible outpatient management
• Repeat ultrasound in the third trimester is suggested if vasa previa is suspected in the second trimester, as approximately 20% of apparent vasa previa will resolve by the late third trimester

SYNOPSIS:

Vasa previa occurs in 1/2500 to 1/5000 pregnancies and is associated with an increased risk of preterm birth and the associated complications of prematurity. There is a 97% survival rate when diagnosed by prenatal ultrasound and a 44% survival rate when the diagnosis is made intrapartum.

KEY POINTS:

• Risk factors:
  • Velamentous cord insertion (Type 1 vasa previa)
  • Succinturate or bilobed placenta connecting vessels (Type 2 vasa previa)
  • Placenta previa or low lying placenta in the second trimester
  • Multiple gestation
  • IVF (1/250 risk of Type 1 vasa previa)
• In cases of low lying placenta, bilobed placenta, succinturate placenta or velamentous cord insertion, a targeted ultrasound for vasa previa should be performed
• Screening possible at 2^nd trimester fetal anatomy ultrasound
  • If detected on 2^nd trimester ultrasound, 20% will resolve
  • Document cord insertion site if possible
• Diagnosis is made by ultrasound, ideally with transvaginal and color flow Doppler
• Ultrasound findings include a linear tubular echolucent body overlying the endocervical os with color flow doppler demonstrating flow through the structure and pulsed doppler showing fetal vascular wave forms
• Risk of perinatal loss due to fetal exsanguination – watch for sinusoidal pattern on FHT tracing
• Plan for delivery at a center that can perform neonatal transfusion if required
  • Note: Center should have negative blood available for neonate in case rapid transfusion is necessary

Learn More – Primary Sources:

SMFM: Diagnosis and management of vasa previa

ACOG/SMFM Committee Opinion 831: Medically Indicated Late-Preterm and Early-Term Deliveries

Society for Maternal-Fetal Medicine (SMFM) Consult Series #44: management of bleeding in the late preterm period

Abnormal Placentation: Placenta Previa, Vasa Previa, and Placenta Accreta

Locate a Maternal Fetal Medicine Specialist:

Maternal-Fetal Medicine Specialist Locator-SMFM

Related ObG Topics:

Placenta Previa – Nomenclature, Diagnosis and Clinical Management

How Effective is Ultrasound in Diagnosing Placenta Accreta?

Latest SMFM Guidelines: Third Trimester Bleeding Between 34w0d and 36w6d Gestation

ACOG Recommendations: When to Deliver Medically Complicated Pregnancies