Vasa praevia

Her membranes rupture at 03:40. There is a modest amount of fresh red blood and her observations are perfect — pulse 78, blood pressure 118/70, no pain. The fetal heart rate falls from 140 to 70 and stays there. She is not the patient who is bleeding. Her baby is, and it has about ten minutes.[4][3]

Overview and definition

Every other cord vessel in pregnancy is protected — wrapped in Wharton's jelly, or buried in placental tissue. In vasa praevia a vessel is neither. It runs bare across the fetal membranes, over or beside the internal cervical os, where the presenting part sits on it and where amniotomy cuts it.[1][3]

• The lesion: fetal vessels in the membranes, unsupported, crossing the cervical os or lying close to it.[1][2]
• The consequence: rupture causes fetal exsanguination; compression causes fetal asphyxia. Either way the mother stays well and her observations stay normal.[4][3]
• The definition boundary: the old rule of thumb was a vessel within 2 cm of the os. The 2024 international Delphi consensus reached agreement that the definition should not be limited to a 2 cm distance, while failing to agree on any single replacement number.[2]

References20Show ledgerHide ledger

1. [1]Jauniaux E, Alfirevic Z, Bhide AG, et al. Vasa Praevia: Diagnosis and Management: Green-top Guideline No. 27b BJOG, 2019.PMID 30260094
2. [2]Oyelese Y, Javinani A, Gudanowski B, et al. Vasa previa in singleton pregnancies: diagnosis and clinical management based on an international expert consensus Am J Obstet Gynecol, 2024.PMID 38494071
3. [3]Oyelese Y, Javinani A, Shamshirsaz AA Vasa Previa Obstet Gynecol, 2023.PMID 37590981
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7. [7]Robinson BK, Grobman WA Effectiveness of timing strategies for delivery of individuals with vasa previa Obstet Gynecol, 2011.PMID 21343756
8. [8]Mitchell SJ, Ngo G, Maurel KA, et al. Timing of birth and adverse pregnancy outcomes in cases of prenatally diagnosed vasa previa: a systematic review and meta-analysis Am J Obstet Gynecol, 2022.PMID 35283090
9. [9]Heyborne K Perinatal Mortality Despite Prenatal Diagnosis of Vasa Previa: A Systematic Review Obstet Gynecol, 2023.PMID 37535966
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13. [13]Ogoyama M, Hasegawa J, Kitada K, et al. Perinatal outcomes among three types of vasa previa: Nationwide survey in Japan Eur J Obstet Gynecol Reprod Biol, 2025.PMID 40706296
14. [14]Buchanan-Hughes A, Bobrowska A, Visintin C, et al. Velamentous cord insertion: results from a rapid review of incidence, risk factors, adverse outcomes and screening Syst Rev, 2020.PMID 32576295
15. [15]Villani LA, Al-Torshi R, Shah PS, et al. Inpatient vs outpatient management of pregnancies with vasa previa: A historical cohort study Acta Obstet Gynecol Scand, 2023.PMID 37537788
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19. [19]Sankaran D, Vali P, Giusto E, et al. Randomised trial of early rapid saline bolus versus epinephrine during resuscitation in perinatal haemorrhagic cardiac arrest in newborn lambs Arch Dis Child Fetal Neonatal Ed, 2026.PMID 41819786
20. [20]Nicolaides KH, Clewell WH, Rodeck CH Measurement of human fetoplacental blood volume in erythroblastosis fetalis Am J Obstet Gynecol, 1987.PMID 3605267