COMPLICATIONS: VASA PREVIA
Vasa previa is one of the lesser-known pregnancy complications — but it's one where early detection genuinely changes everything. If you've received this diagnosis, or you're reading ahead to understand what it means, here's what you and your partner need to know.
What Is Vasa Previa?
To understand vasa previa, it helps to start with the umbilical cord. Under normal circumstances, the blood vessels that run from the placenta to your baby travel safely through the cord, cushioned by a protective substance called Wharton's jelly. In vasa previa, some of these fetal blood vessels travel outside of that protection — unsupported by either the cord or the placenta — and pass directly over the cervix, covered only by the fragile amniotic membranes.
That positioning creates a specific, serious risk: if those membranes rupture — whether naturally in labor, or artificially during an induction — the exposed vessels can tear with them. Because these are fetal blood vessels, a rupture means the baby loses blood rapidly. Given that a baby's entire blood volume is only around 275ml, the situation can become critical very quickly.
This is why vasa previa is treated with such urgency by obstetric teams. When it isn't detected before labor, the outcomes can be devastating. When it is detected in time, they are almost entirely preventable.
There are two main types:
Type I — caused by a velamentous cord insertion, where the umbilical cord attaches to the membranes rather than the placenta, with vessels running freely from that point
Type II — occurs when a bilobed or multi-lobed placenta has vessels connecting the lobes that run across the cervix
How Common Is It, and Who Is at Risk?
Vasa previa affects roughly 1 in 2,500 pregnancies in the general population. That said, the rate rises significantly in certain groups — particularly for people who conceived through IVF, where the incidence is closer to 1 in 250.
Other risk factors include:
Velamentous cord insertion (where the cord inserts into the membranes rather than directly into the placenta)
A bilobed or succenturiate placenta (a placenta with an extra lobe)
Low-lying placenta or placenta previa during the second trimester, even if it subsequently resolves
Multiple pregnancy (twins or more)
Previous uterine surgery
Having one or more of these factors doesn't mean vasa previa will occur, but it does mean your care team should be looking specifically for it.
When and How Is It Diagnosed?
Most cases of vasa previa are identified during the mid-trimester anatomy scan, typically at 18–22 weeks. Diagnosis is made using color flow Doppler ultrasound, a technique that maps blood flow and can show vessels crossing the cervix. A transvaginal ultrasound (TVS) is often used alongside the standard abdominal scan, as it provides a much clearer picture of the area around the cervix.
The detection rate with this approach is high, around 93–98% in centres that screen routinely. However, not all hospitals include vasa previa in their standard screening protocol, which is one reason some cases are still missed. If you have known risk factors, it is absolutely reasonable to ask your care team whether the cord insertion site and the area around your cervix have been specifically assessed.
If a suspected finding is made at 20 weeks, your team will arrange a follow-up scan, usually around 23, to confirm the diagnosis, as a small number of early findings do resolve. Once confirmed in the third trimester, the diagnosis stands and management begins in earnest.
Why Does Early Diagnosis Matter So Much?
The difference in outcomes between diagnosed and undiagnosed vasa previa is stark — and it's worth being direct about, because it underscores why this diagnosis, though alarming to receive, is actually a protective one.
In cases where vasa previa is not diagnosed before labor, the fetal mortality rate has historically been reported at 40–60%. The vessels rupture without warning when the membranes break, and there is rarely enough time to respond.
In cases where vasa previa is diagnosed prenatally and managed appropriately, survival rates are over 95–97%. The condition is not cured by diagnosis, but it is entirely manageable when known about in advance.
As one maternal-fetal medicine specialist has put it: there are very few conditions in obstetrics where prenatal diagnosis makes such a profound difference to whether a baby lives or dies.
If you've just received this diagnosis, that context matters: your care team now knows what they're dealing with, and that knowledge is what protects your baby. (But yes, it still sucks & is very scary to get this diagnosis).
Management: What Happens Now?
Once vasa previa is confirmed, your care shifts to specialist-led monitoring with a clear plan for the weeks ahead.
Surveillance and Specialist Care
You will likely be referred to (or already under the care of) a maternal-fetal medicine specialist. Regular ultrasounds will monitor the position of the vessels. Your team will also assess your cervix, a shorter cervical length is associated with higher risk of preterm labor and early membrane rupture, which becomes particularly important with vasa previa.
Antenatal Corticosteroids
A course of corticosteroid injections is recommended between 28 and 32 weeks. These are given to accelerate your baby's lung development, in preparation for the possibility of preterm delivery. This is standard management, not a sign that things are going wrong, it's proactive preparation.
Hospitalization
Depending on your specific circumstances, your obstetrician may recommend hospitalization from around 30–34 weeks. This is not a universal recommendation, it depends on factors including whether you've had any bleeding or contractions, how close to a specialist maternity unit you live, and whether preterm labor is considered a risk.
For many people, the prospect of extended hospital admission is daunting, and it comes with real disruptions to work, family, and day-to-day life. It can help to discuss the reasoning in detail with your team, understanding exactly what they're watching for, and what the specific threshold for intervention would be, can make the situation feel less uncertain.
What to Avoid
You will need pelvic rest, so avoid vaginal intercourse, strenuous exercise, tampon usage (etc). Any activity that might put pressure on the cervix or stimulate contractions should be discussed with your care team.
Emergency Presentation
If at any point you experience vaginal bleeding, contractions, or your water breaks, this is an emergency. Go immediately to your nearest maternity unit. Do not wait to see if bleeding stops. Do not drive yourself if your partner or someone else can take you.
Delivery: Planning a Caesarean
A planned caesarean section is the standard delivery method for vasa previa. A vaginal birth is not safe because any rupture of the membranes, even the gentle, gradual rupture that often begins labor, puts the unprotected vessels at risk.
The timing is typically 34–37 weeks, with most guidelines recommending somewhere around 34–36 weeks. The exact timing involves weighing two things: the risk of early delivery (and the mild prematurity that comes with it) against the risk of spontaneous membrane rupture as pregnancy progresses. Your team will guide this decision based on your individual circumstances — cervical length, any history of bleeding or contractions, and how your pregnancy is progressing overall.
The delivery needs to take place at a hospital equipped to provide immediate neonatal blood transfusion, in case the baby requires it. Negative blood type should be available on standby. This is a logistical precaution, not a prediction.
Approximately 28% of people with prenatally diagnosed vasa previa end up requiring an emergency caesarean before their planned date, due to bleeding, contractions, or early rupture. This is another reason close monitoring and, for some people, hospitalization near the end of pregnancy makes sense.
The Implications for Your Baby
Babies born via planned caesarean for vasa previa are typically born in the late preterm period (34–37 weeks). At this stage, most are healthy and require only standard newborn care, though some may need a brief period of support for breathing or feeding as is normal for late preterm births. This can require a NICU stay, so it’s also helpful to speak to a neonatologist for what that could look like.
In the small number of cases where there has been some bleeding before or during delivery, the neonatal team will be ready to provide a blood transfusion if needed. This preparation is what turns a potentially dangerous situation into a manageable one.
The long-term outcomes for babies diagnosed and managed well are excellent. This is a condition where the medical system, when informed, can genuinely protect your child.
The Emotional Weight of This Diagnosis
Finding out you have vasa previa is frightening. The statistics that come with it, particularly around undiagnosed cases, are scary to read. It's natural to feel anxious, hyperaware of every sensation in your body, and worried about what might happen.
A few things that can help:
Remember what the diagnosis means. Receiving a vasa previa diagnosis is a genuinely good outcome compared to the alternative of not knowing. Your care team can now act. That's not a small thing.
Ask specific questions. Which type of vasa previa do you have? How close are the vessels to the cervix? What is your cervical length? What is the plan, week by week, from here? Concrete information tends to reduce anxiety more than general reassurance.
Include your partner. This is a diagnosis that affects both of you. Attending scans and appointments together, and understanding the plan as a team, helps both partners feel less helpless and more prepared.
Connect with others who've been here. Organisations like the International Vasa Previa Foundation offer peer support from people who have navigated this exact situation. Talking to someone who has come through it, who held their baby after a planned caesarean and went home, can be worth more than any article.
Grieve the birth you imagined, if you need to. It's okay to feel loss around a change in your birth plan. A planned caesarean at 35-36 weeks is not the birth many people envisioned, and those feelings are valid. And it is also an extraordinary act of care for your baby.
What to Watch For
Contact your doctor/hospital immediately if you experience any of:
Vaginal bleeding, no matter how light
Your waters breaking or a gush or trickle of fluid
Regular contractions or cramping before your planned delivery date
Reduced or absent fetal movement
Any feeling that something is wrong
With vasa previa, "wait and see" is not an approach. Always call.
The Bottom Line
Vasa previa is rare, serious, and when known about in advance,very manageable. The transformation in outcomes that comes from a prenatal diagnosis is one of the clearest examples in modern obstetrics of how monitoring and preparation save lives. The plan your care team puts in place, specialist oversight, corticosteroids, a carefully timed caesarean, exists precisely to get you and your baby through this safely.
Post Script: Jill, co-founder of Labour the App, had vasa previa with her second child (many tears were shed on the day of diagnosis). If you want to reach out to her about this diagnosis, email her at jill@labourtheapp.com.
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