Vasa praevia

What is vasa praevia?  

In most pregnancies the blood vessels that bring oxygen and blood to your baby are protected within the umbilical cord or placenta. In vasa praevia a section of these vessels is not protected. Instead, they pass near or over your cervix, under your baby.

As the blood vessels are not protected, and because they are very delicate, they can tear during labour or when your waters break. This can be dangerous because the blood that is lost comes from your baby. Babies only have a small amount of blood in their bodies so losing blood can make them very unwell. Sadly, up to 6 in 10 affected babies who lose blood in this way die.

It is important to remember that vasa praevia is a very rare condition affecting between 1 in 1200 and 1 in 5000 pregnancies.

What causes vasa praevia? 

We do not know exactly why vasa praevia happens. But we know the risk of having it is higher if: 

• your placenta or umbilical cord develops in an unusual way  
• you have a low-lying placenta 
• you are carrying more than one baby 
• you are having an IVF pregnancy. 

Having vasa praevia in a previous pregnancy does not mean you are more likely to get it again.

How is vasa praevia diagnosed? 

The UK national screening committee does not recommend that all women and birthing people be screened for vasa pravia in pregnancy because:  

• it is not known how many babies are affected by it in the UK 
• it is not known how accurate screening tests are at detecting it 
• screening may mean some women and birthing people are offered an early caesarean section when they do not need one 
• some people may be reassured by false tests and still have a problem during delivery. 

If you have risk factors 

If your midwife or doctor thinks you may be at risk of vasa praevia they may offer you an extra scan during your pregnancy to check whether you have it.

If your doctor thinks you have vasa praevia in your first or second trimester, they may offer you a transvaginal scan at your appointment, then another scan during your third trimester to confirm it.

A transvaginal ultrasound means ‘through the vagina’. Your healthcare professional will gently insert a small ultrasound probe into your vagina. This has a sterile (clean) cover. An images of your cervix (womb) are then shown on a monitor. 

Internal examinations may be uncomfortable, but not painful.

Vasa praevia symptoms 

Some people do not get any symptoms of vasa praevia. Others may have some vaginal bleeding. If you have any vaginal bleeding during your pregnancy, with or without pain, it is always important to get it checked out straight away. 

You may also be diagnosed with vasa praevia during early labour if: 

• you have a vaginal examination that reveals vasa praevia 
• you have vaginal bleeding 
• your baby is in distress after your waters break.

If you have any bleeding during your pregnancy, with or without pain, it’s very important to get it checked out.

You should also tell your maternity unit right away if your waters break and:  

• the fluid is smelly, tinged or coloured 
• you are losing blood. 

This could mean you and your baby need urgent attention.

Being diagnosed with vasa praevia during pregnancy can be worrying but most babies survive if doctors diagnose vasa praevia before labour begins. 

How is vasa praevia treated? 

If your healthcare professional confirms vasa praevia before you go into labour, they will recommend that your baby is born by planned caesarean section at around 34–36 weeks of pregnancy 

This means that your baby will be born prematurely, so your medical team will recommend that you have a course of steroids (two injections, 12–24 hours apart) to help your baby’s lungs and other organs to mature. This is likely to be in the week before your planned caesarean. 

Some people may also need to stay in hospital from around 30 to 32 weeks of pregnancy, until their baby is born. You may be asked to stay in hospital if you: 

• are having more than one baby 
• have any vaginal bleeding 
• are at risk of going into premature labour. 

If your midwife or doctor suspects you may have vasa praevia when you go into labour or when your waters break, they will explain that your baby needs to be born urgently, usually by emergency caesarean.  

Sometimes, babies need resuscitation or blood transfusions to help them survive vasa praevia in labour. This can be a scary experience, but you will be in the right place, and your medical team will be fully prepared to treat your baby.   

Can I do anything to prevent vasa praevia? 

Unfortunately, there is no way to stop vasa praevia from happening. However, your baby’s chances of survival are high if it is diagnosed during pregnancy. 

Making sure that you go to all your ultrasound scans and antenatal appointments will help to make sure you are doing the best you can for your baby. Always let your midwife or doctor know if you have any symptoms that you are concerned about.  

You can contact our midwives if you have a question or if you feel like you need some extra support. Call us free on 0800 014 7800 (Monday to Friday, 9am to 5pm) or email us at [email protected].