Vasa previa
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At the time the article was created Yuranga Weerakkody had no recorded disclosures.
View Yuranga Weerakkody's current disclosuresAt the time the article was last revised Arlene Campos had no financial relationships to ineligible companies to disclose.
View Arlene Campos's current disclosures- Vasa previa
Vasa previa refers to a situation where there are aberrant fetal vessels crossing over or in close proximity to the internal cervical os, ahead of the fetal presenting part. These vessels are within the amniotic membranes, without the support of the placenta. Vasa previa is a rare but potentially catastrophic cause of antepartum hemorrhage.
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Epidemiology
Vasa previa occurs in 0.6 per 1000 pregnancies 11.
Risk factors
IVF pregnancy
Clinical presentation
Prior to rupture of the amniotic membrane during labor, compression of the vulnerable fetal blood vessels by the presenting part may lead to fetal heart decelerations and bradycardia.
However once ruptured, vasa previa will result in brisk vaginal bleeding with rapid fetal exsanguination.
Pathology
Vasa previa can be of two types:
type I (~90% 3): abnormal fetal vessels connect a velamentous cord insertion with the main body of the placenta
-
type II
abnormal vessels connect portions of a bilobed placenta
placenta with a succenturiate lobe: due to this association, vasa previa needs to be excluded in patients with variant placental morphology
These vessels are unsupported by Wharton jelly or placental tissue and are at risk of rupture during labor.
Radiographic features
Ultrasound
Sonographic features are considered generally specific (~90%) 2.
The diagnosis is often made with transabdominal color Doppler sonography demonstrating flow within vessels that are seen overlying the internal cervical os. Greyscale images may suggest the diagnosis if there are echogenic parallel or circular lines within the placenta near the cervix.
Occasionally a transvaginal scan is required to better visualize aberrant vessels. Transvaginal ultrasound has a reported sensitivity of 100% and specificity of 99-99.8% when performed with color Doppler 12.
Treatment and prognosis
If recognized antenatally, vasa previa usually requires an elective cesarean section to avoid the risk of complications during vaginal delivery.
If recognized intrapartum, an emergency cesarean section is usually performed.
Differential diagnosis
On antenatal ultrasound consider:
marginal placenta previa: where prominent maternal vessels are appreciated at the edge of the placenta
References
- 1. Fadl S, Moshiri M, Fligner CL, Katz DS, Dighe M. Placental Imaging: Normal Appearance with Review of Pathologic Findings. Radiographics : a review publication of the Radiological Society of North America, Inc. 37 (3): 979-998. doi:10.1148/rg.2017160155 - Pubmed
- 2. Catanzarite V, Maida C, Thomas W et-al. Prenatal sonographic diagnosis of vasa previa: ultrasound findings and obstetric outcome in ten cases. Ultrasound Obstet Gynecol. 2001;18 (2): 109-15. doi:10.1046/j.1469-0705.2001.00448.x - Pubmed citation
- 3. Hasegawa J, Farina A, Nakamura M et-al. Analysis of the ultrasonographic findings predictive of vasa previa. Prenat. Diagn. 2010;30 (12-13): 1121-5. doi:10.1002/pd.2618 - Pubmed citation
- 4. Lee W, Lee VL, Kirk JS et-al. Vasa previa: prenatal diagnosis, natural evolution, and clinical outcome. Obstet Gynecol. 2000;95 (4): 572-6. - Pubmed citation
- 5. Hertzberg BS, Kliewer MA. Vasa previa: prenatal diagnosis by transperineal sonography with Doppler evaluation. J Clin Ultrasound. 1998;26 (8): 405-8. J Clin Ultrasound (link) - Pubmed citation
- 6. Nimmo M, Kinsella D, Andrews H. MRI in Pregnancy: The Diagnosis of Vasa Previa by Magnetic Resonance Imaging. Bristol Med Chir J. 1988;103(2):12. PMC5113616 - Pubmed
- 7. Oyelese Y, Jha RC, Moxley MD et-al. Magnetic resonance imaging of vasa praevia. BJOG. 2003;110 (12): 1127-8. BJOG (link) - Pubmed citation
- 8. Gagnon R, Morin L, Bly S et-al. Guidelines for the management of vasa previa. J Obstet Gynaecol Can. 2009;31 (8): 748-60. - Pubmed citation
- 9. Edward I. Bluth. Ultrasound. (2000) ISBN: 9780865778610 - Google Books
- 12. Ruiter L, Kok N, Limpens J et al. Incidence of and Risk Indicators for Vasa Praevia: A Systematic Review. BJOG. 2016;123(8):1278-87. doi:10.1111/1471-0528.13829 - Pubmed
- 12. Ruiter L, Kok N, Limpens J et al. Systematic Review of Accuracy of Ultrasound in the Diagnosis of Vasa Previa. Ultrasound Obstet Gynecol. 2015;45(5):516-22. doi:10.1002/uog.14752 - Pubmed
- Carol B. Benson, Edward I. Bluth. Ultrasonography in Obstetrics and Gynecology. (2008) ISBN: 9781588906120 - Google Books
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