What is vasa previa?
Vasa previa is a condition in which unprotected fetal blood vessels run through the membranes across or near the cervix (directly in the path of delivery) where they can tear when the membranes rupture, causing the baby to bleed rapidly. Normally the baby’s vessels are shielded inside the umbilical cord and cushioned by Wharton’s jelly. In vasa previa, some of those vessels travel exposed across the lower part of the uterus, unsupported by the cord or placenta. Because the blood in those vessels is the baby’s own, and a baby has only a small total blood volume, even a small tear can be fatal within minutes.
This is one of the four conditions under our umbilical cord complications hub, and it is the one where the gap between diagnosed and undiagnosed outcomes is starkest. Vasa previa is rare (roughly 1 in 2,500 births) but it is the clearest example in obstetrics of a condition where prenatal screening turns a near-certain tragedy into a routinely survivable one.
Why undiagnosed vasa previa is catastrophic
We state this plainly because it is the heart of the matter. When vasa previa is not diagnosed before labor, the outcomes are devastating: studies have historically reported fetal survival rates well below half when the condition is discovered only after the vessels tear. The reason is the mechanism. When the membranes rupture (spontaneously or when a provider breaks them) the exposed vessels can tear at the same moment, and the baby exsanguinates (bleeds out) into the amniotic fluid. There is rarely time to intervene, because a baby’s entire blood volume is small and the loss is fast. A related danger is that the vessels can be compressed by the descending baby even without tearing, cutting off oxygen. This is why undiagnosed vasa previa is one of the most catastrophic cord conditions there is.
Risk factors
Vasa previa is strongly associated with identifiable risk factors, which is precisely what makes screening possible. They include:
- Low-lying placenta or placenta previa in the second trimester, even if it later resolves
- Velamentous cord insertion: the cord inserting into the membranes rather than the center of the placenta
- A bilobed or succenturiate-lobed placenta (an extra placental lobe), where connecting vessels can cross the membranes
- Pregnancy from in-vitro fertilization (IVF)
- Multiple gestation (twins or more)
Because these factors are known during routine prenatal imaging, they give clinicians a clear opportunity (and, in the presence of risk factors, a responsibility) to look specifically for vasa previa.
Did a low-lying placenta or velamentous cord insertion in your records prompt a look for vasa previa? When risk factors were present and screening was not done, an undiagnosed vasa previa can be the difference between a planned cesarean and a tragedy. Our attorneys review your imaging and records with you at no cost.
Ultrasound screening standards
Vasa previa can be diagnosed before birth. The standard tool is transvaginal ultrasound with color Doppler, which shows the fetal vessels crossing the membranes over or near the cervix. Professional guidance directs clinicians to evaluate for vasa previa when risk factors are present (such as a low-lying or previa placenta on the anatomy scan, a velamentous cord insertion, or a bilobed placenta) and to confirm suspected cases with transvaginal color Doppler. When a low-lying placenta is noted earlier in pregnancy, follow-up imaging should reassess the placental position and cord insertion. The failure to look for vasa previa in a patient with clear risk factors, or to act on findings that suggest it, is the central issue in many of these claims.
Planned cesarean management
When vasa previa is diagnosed in advance, management is well established and highly effective. It generally includes:
- Corticosteroids around 28 to 32 weeks to mature the baby’s lungs in anticipation of an early delivery
- Consideration of hospital admission in the third trimester for close monitoring, so a rupture or bleeding can be responded to immediately
- A scheduled cesarean delivery before labor begins and before the membranes rupture (commonly in the mid-to-late 30s of gestational weeks) so the exposed vessels are never put at risk
The entire strategy rests on delivering the baby by cesarean before the membranes can rupture. Done this way, vasa previa is highly survivable.
Outcomes: the diagnosis makes the difference
Few conditions show such a stark divide. Diagnosed prenatally and managed with a planned cesarean, neonatal survival is very high, commonly reported at 97% or better. Undiagnosed, survival has historically been far lower, and survivors may face injury from blood loss or oxygen deprivation, including hypoxic-ischemic encephalopathy (HIE) and its consequences. The single variable that most determines the outcome is whether the condition was found before labor. That is what makes vasa previa, more than almost any other cord problem, a screening-and-diagnosis story.
Was the harm preventable?
An undiagnosed vasa previa can be an unpreventable tragedy, though in many cases the harm was preventable through screening. When risk factors were present on prenatal imaging and vasa previa was not looked for, or when findings that pointed to it were not acted on, a condition that is routinely survivable was allowed to become catastrophic. The failures that lead to injury are recognizable: a low-lying placenta or velamentous cord insertion that never prompted a targeted look, a missed diagnosis on imaging, or a failure to plan a cesarean once vasa previa was known. The question a records review answers is whether the standard of care for screening and management was met.
Legal options for families
A vasa previa claim is a medical-negligence claim, and it usually turns on diagnosis. It asks whether your providers screened for vasa previa when the risk factors called for it, correctly interpreted the imaging, and planned delivery to protect the baby, and whether a failure caused a preventable loss or injury. Where a baby suffered brain injury from oxygen or blood loss, compensation may need to cover a lifetime of care; our guide to compensation in HIE cases explains how those cases are valued. It can help to understand related cord conditions, including cord prolapse and true knots. Filing deadlines (statutes of limitations) vary by state, so confirm them early.
Where your case would be handled depends on where the care happened. Banville Law attorneys are licensed in New York and Washington, D.C.; The Weitz Firm attorneys are licensed in Pennsylvania and New Jersey. Everywhere else, the alliance connects families with its vetted network of local birth injury attorneys. Special rules apply to care at military or federally funded hospitals.
Frequently asked questions
Can vasa previa be detected before birth?
Yes. Vasa previa can be diagnosed with transvaginal ultrasound and color Doppler, which show the fetal vessels crossing the membranes near the cervix. Guidance directs clinicians to look for it when risk factors are present, such as a low-lying placenta, a velamentous cord insertion, or a bilobed placenta. This is why screening is so important.
Why is undiagnosed vasa previa so dangerous?
Because the exposed fetal vessels can tear the moment the membranes rupture, and a baby’s total blood volume is small, so the loss is rapid and often fatal within minutes. There is rarely time to intervene once bleeding starts. Diagnosed in advance, the same condition is routinely survivable with a planned cesarean.
How is diagnosed vasa previa managed?
With a planned, scheduled cesarean before labor and before the membranes can rupture (commonly in the mid-to-late 30s of gestational weeks) often preceded by corticosteroids to mature the baby’s lungs and, in many cases, third-trimester hospital admission for close monitoring.
What are the survival rates for vasa previa?
The difference is dramatic. Diagnosed prenatally and delivered by planned cesarean, neonatal survival is commonly reported at 97% or higher. Undiagnosed, historical survival rates have been far lower, and survivors may face injury from blood loss or oxygen deprivation. The diagnosis is the single biggest factor in the outcome.
Sources
- Society for Maternal-Fetal Medicine (SMFM); Sinkey RG, et al. Diagnosis and Management of Vasa Previa. American Journal of Obstetrics & Gynecology. 2015;213(5):615–619.
- Oyelese Y, et al. Vasa previa: the impact of prenatal diagnosis on outcomes. Obstetrics & Gynecology. 2004;103(5):937–942.
- Ruiter L, et al. Systematic review of accuracy of ultrasound in the diagnosis of vasa previa. Ultrasound in Obstetrics & Gynecology. 2015;45(5):516–522.
- American College of Obstetricians and Gynecologists. Guidance on placenta previa, low-lying placenta, and vasa previa, in Williams Obstetrics, 26th ed. McGraw Hill, 2022.
This page is for general education and is not medical advice. Medical facts above are drawn from the cited primary sources; legal statements reflect the reviewing attorneys’ professional experience. Always consult your physician about medical concerns.