Vasa Previa

Aka: Vasa Previa, Ruptured Vasa Previa

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II. Definitions

  1. Vasa Previa
    1. Cord velamentous membrane insertion near cervical os
    2. Fetal blood vessels cross presenting membranes
    3. Vessels may also traverse the Cervix when bridging between a bilobed placenta

III. Pathophysiology

  1. Blood loss is primarily from fetus
    1. Entire fetal Blood Volume is 300 ml at term
    2. Vasa Previa rupture may cause rapid fetal Exsanguination with high morbidity and mortality
  2. Abnormal fetal vessel insertion
    1. Fetal vessels unsupported by placenta
    2. Velamentous insertion at membranes, not at placenta
    3. Fetal vessels in membranes and tranverse Cervix

IV. Epidemiology

  1. Rare cause of Late Pregnancy Bleeding
  2. Incidence: 1 in 2500 pregnancies

V. Risk Factors

  1. Low-lying placenta in second trimester
  2. In Vitro fertilization (IVF)
  3. Bilobed or succenturiate lobe of placenta
  4. Multiple Pregnancy (e.g. Twin Gestation)

VI. Findings: Symptoms and signs

  1. Presentation
    1. Vaginal Bleeding immediately after membrane rupture
    2. Vessel may be palpable on cervical exam
  2. Fetal Distress
    1. Late Decelerations
    2. Sinusoidal Fetal Heart Rate pattern
    3. Fetal Bradycardia

VII. Labs: Only in stable cases

  1. Modified Apt Test
  2. Wright's stain

VIII. Imaging

  1. Ultrasound indications
    1. Routinely on Second Trimester Ultrasound
    2. Ultrasound at 32 weeks gestation
      1. Ultrasound with placental previa (or resolved Placenta Previa)
      2. Low lying placenta
  2. Transvaginal Ultrasound with color flow doppler
    1. Differentiate from Umbilical Cord
    2. Consider in stable cases with suspected Vasa Previa
    3. Not indicated for general screening

IX. Management: Emergent

  1. See Late Pregnancy Bleeding
  2. Heavy bleeding or non-reassuring Fetal Heart Tones
    1. Requires immediate delivery
    2. Do not delay delivery for labs or Ultrasound
  3. Immediate fluid resucitation of fetus on delivery
    1. IV or umbilical line: 10-20 cc NS bolus

X. Management: Routine

  1. Consult maternal fetal medicine
  2. Consider prenatal Corticosteroids if Gestational Age <34 weeks (esp. 28 to 32 weeks)
  3. Delivery by Cesarean Section at 34 to 37 weeks

XI. Prognosis

  1. High perinatal mortality from fetal Exsanguination: 50%
  2. Neonatal survival without Hypoxia complications is 97% with a antenatal Vasa Previa diagnosis
    1. Vasa Previa may be diagnosed routinely on Second Trimester Ultrasound
    2. Contrast with 28% when diagnosis is delayed until after membrane rupture

XII. Resources

  1. Vasa Previa Foundation
    1. http://vasaprevia.org

XIII. References

  1. Lee (2000) Obstet Gynecol 95:572-6 [PubMed]
  2. Sakornbut (2007) Am Fam Physician 75:1199-206 [PubMed]
  3. Yonke (2025) Am Fam Physician 112(6): 638-45 [PubMed]

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