Placenta Praevia

If you've been told that your placenta is low-lying, or that you have placenta praevia, it's understandable if your mind immediately jumps to questions about bleeding, caesarean birth and what this means for your pregnancy. The good news is that most low-lying placentas found at the 20-week scan don't stay low throughout pregnancy. As your uterus grows, the placenta often ends up further away from the cervix. Here's what placenta praevia means, what happens if your placenta is low-lying, and what you might expect from the rest of your pregnancy.

What is Placenta Praevia?

The placenta attaches to the wall of your uterus during pregnancy. It provides your baby with oxygen and nutrients and is delivered shortly after your baby is born. Sometimes the placenta attaches in the lower part of the uterus, close to the cervix. A low-lying placenta is usually described as the placenta being less than 20mm from the cervix. Placenta praevia is when the placenta completely covers the cervix. The cervix is the opening at the bottom of your uterus that needs to open during labour so that your baby can be born. If the placenta is covering the cervix, it can block the baby's route out and can also cause significant bleeding, particularly later in pregnancy.

How Common is it?

A low-lying placenta is fairly common at the 20-week scan. The important thing to know is that finding a low-lying placenta at 20 weeks doesn't necessarily mean you'll have placenta praevia at the end of your pregnancy. Around 9 out of 10 women who have a low-lying placenta at their 20-week scan will find that it is no longer low at their follow-up scan. Placenta praevia at the end of pregnancy affects around 1 in 200 births. So if you've been told your placenta is low at your 20-week scan, there's a good chance that this won't be where it ends up.

Why Does the Placenta "Move"?

Technically, the placenta doesn't usually get up and move around the uterus. Instead, as your uterus grows and changes shape during pregnancy, the area around the placenta stretches and develops. This can mean that the placenta ends up further away from the cervix.

Think of it a little like putting a sticker on a balloon and then inflating the balloon. The sticker hasn't walked anywhere, but its position in relation to the rest of the balloon has changed.

How is Placenta Praevia Diagnosed?

The position of your placenta is routinely checked during your 20-week ultrasound scan. If your placenta is found to be low-lying, you'll usually be offered another scan at around 32 weeks to check its position again. This may include a transvaginal ultrasound scan. If the placenta is still low at this stage, you'll usually be offered another scan at around 36 weeks. A transvaginal ultrasound can sound alarming if you've never had one before, but it is considered safe during pregnancy and can give a much more accurate picture of how close the placenta is to your cervix.

Can Placenta Praevia Cause Bleeding?

Yes. Bleeding caused by placenta praevia is often painless and bright red, and it can happen in the second half of pregnancy. It can sometimes happen after sex. Importantly, bleeding with placenta praevia can occasionally be sudden and heavy. If you have been told that you have a low-lying placenta or placenta praevia and you experience any vaginal bleeding, contractions or pain, contact your maternity unit straight away. Any bleeding in pregnancy should be taken seriously. You can read more about when to seek help in pregnancy here: When to Seek Help

Does Having Placenta Praevia mean I'll need a Caesarean?

If the placenta is still covering the cervix towards the end of pregnancy, a caesarean birth will usually be recommended because the placenta is blocking the baby's route through the vagina. If the placenta is low-lying rather than covering the cervix, the distance between the placenta and the cervix matters. RCOG guidance states that if the edge of the placenta is less than 20mm from the cervix at the 36-week scan, caesarean birth is considered the safest way to give birth. If it is more than 20mm away, a vaginal birth may be possible.

Your individual circumstances matter too, including whether you've experienced bleeding during pregnancy and exactly where the placenta is positioned. So being told you have a low-lying placenta at 20 weeks does not automatically mean that you will have a caesarean.

When would a Planned Caesarean Happen?

If you have placenta praevia and haven't had heavy or recurrent bleeding, a planned caesarean will usually be around 36 to 37 weeks.

If you've had significant bleeding, your baby may need to be born earlier. Because placenta praevia can cause heavy bleeding, your maternity team will plan your birth with this possibility in mind. This may include making sure appropriate blood products and specialist staff are available if they are needed. If your placenta is still low-lying, your maternity team should talk through your individual situation and your options with you rather than simply giving you a date and sending you on your way.

What Happens if I have no Bleeding?

You may have no symptoms at all. Some people with placenta praevia experience bleeding during pregnancy, while others don't.

Even without previous bleeding, there is a small risk of sudden heavy bleeding later in pregnancy. Your care team will therefore consider your individual circumstances when deciding how closely you need to be monitored and whether you need to stay in hospital towards the end of pregnancy. You may also have additional blood tests to monitor your haemoglobin and help make sure that you're not anaemic.

This is one reason why keeping your iron levels in good shape can be particularly important if you have a low-lying placenta.

Explore next: Anaemia in Pregnancy

Is Placenta Praevia More Common after a Caesarean?

Yes. Previous caesarean birth is one of the factors associated with a higher chance of placenta praevia. It is also associated with factors including fertility treatment and smoking. If you have placenta praevia alongside a previous caesarean birth, your care team may also consider the possibility of placenta accreta spectrum, where the placenta becomes abnormally attached to or grows into the muscle of the uterus. This is a separate condition, but the two can occur together. The updated RCOG guidance published in 2026 also recognises that placenta accreta spectrum can be associated with other types of previous uterine surgery, not just caesarean birth. If this is relevant to you, your maternity team may arrange additional specialist scans and care.

What About my Birth Preferences?

Being diagnosed with placenta praevia can mean that some of the birth plans you had imagined may need to change. If the placenta remains over or very close to your cervix, a vaginal birth may not be safe. But there can still be plenty of things that are within your control. You can ask about:

Where your birth will take place
Who will be involved in your care
When and why a planned caesarean is being recommended
What would happen if you went into labour before your planned date
What would happen if you experienced bleeding
Your options for anaesthesia
Whether your birth partner can be with you
What happens immediately after your baby is born
Feeding and skin-to-skin after birth
How your individual preferences can still be incorporated into your caesarean birth

A caesarean birth may be the safest way for your baby to be born, but that doesn't mean you have to stop thinking about the experience of your birth. Explore next: Caesarean Birth

A note about Exercise, Sex and everyday life

If you've been diagnosed with a low-lying placenta, you may understandably wonder whether you need to stop doing things such as exercise, yoga or having sex. There isn't one blanket answer for everyone. Your advice may depend on exactly where your placenta is, whether you've had any bleeding or contractions, and how far through pregnancy you are. If you've been given specific restrictions by your maternity team, follow those and ask if you're unsure why they're needed. If you haven't been given individual advice, it's worth asking your midwife or obstetrician what is appropriate for you rather than assuming that a diagnosis automatically means you need to put your feet up for the rest of pregnancy.

Questions you Might Want to Ask

If you've been told your placenta is low-lying, you might find it useful to ask:

How far is my placenta from my cervix?
Is it low-lying or covering the cervix?
When will I have another scan?
Will I need a transvaginal scan?
Do I need any restrictions on exercise or activity?
Is there any advice about sex?
What should I do if I experience bleeding?
Do I need to contact my maternity unit directly if I have any bleeding?
Where will I give birth?
If the placenta remains low, what does this mean for my options for birth?
If I need a caesarean, when would you recommend it and why?
Are there any other reasons you want to monitor me or my baby more closely?

You don't have to remember all of these. Pick the questions that are relevant to you and take them to your next appointment.

Explore Next

When to Seek Help
What pregnancy symptoms need checking, and when to contact your maternity team.

Ultrasound Scans
What happens during pregnancy scans and what they can and can't tell you.

Anaemia in Pregnancy
Why keeping an eye on your haemoglobin can be particularly important when there's a risk of bleeding.

Caesarean Birth
Understanding what a planned caesarean involves and the choices you may still have around your birth.

Understanding Your Options
More resources to help you understand recommendations and make informed decisions about your care.