Placenta Praevia (Low lying placenta)
In most pregnancies, the placenta attaches to the front or back of the womb (the uterus). But sometimes it attaches lower down and may cover a part or all of the cervix (the entrance to the womb).
Placenta Praevia (Low lying placenta) Information
What is the placenta?
The placenta is the organ that helps your baby grow and develop. It’s attached to the lining of the womb and is connected to your baby by the umbilical cord. The placenta passes oxygen, nutrients and antibodies from your blood supply to your baby. It also carries waste products from your baby to your blood supply, so your body can get rid of them.
What is a low-lying placenta?
The placenta develops in the first few weeks of pregnancy, wherever the fertilised egg embeds itself. This could be along the top, sides, front or back wall of the womb.
In most pregnancies the placenta attaches to the main part of the womb. But for some women, the placenta attaches lower down and may cover some or all of the cervix (entrance to the womb).
In most cases of a low-lying placenta, the placenta moves upwards and out of the way as the uterus grows during pregnancy.
What is the difference between a low-lying placenta and placenta praevia?
As the pregnancy continues, if the edge of the placenta is less than 2mm from the cervix, it is known as a low-lying placenta. If the placenta completely covers the cervix, it is known as placenta praevia.
Is a low-lying placenta common?
The position of your placenta will be checked at your mid-trimester ultrasound scan, at around 18-21 weeks of pregnancy. If your placenta is low-lying, you have another scan later in your pregnancy (usually about 32 weeks).
Because the lower part of the womb stretches more as the baby grows, the placenta usually moves into the upper part of the womb by this point. 90% of women who have a low-lying placenta at 20 weeks will not go on to have a low-lying placenta later in the pregnancy.
If you have had a baby by caesarean section before, the placenta is less likely to move upwards.
Only 1 in every 200 women have placenta praevia at the end of their pregnancy.
Am I likely to have placenta praevia?
Placenta praevia is more likely if you:
- smoke cigarettes
- have had fertility treatment to get pregnant, such as in vitro fertilisation (IVF)
- have had 1 or more caesarean sections
- are aged 40 or older
- are having more than 1 baby
- have had surgery on the womb
- are a cocaine user
- are expecting a boy
- have endometriosis.
Is there anything I can do to help the placenta move up?
Unfortunately not. The best thing you can do is concentrate on staying as healthy as you can. You may need extra scans, so make sure you go to all your antenatal appointments and follow your healthcare professional’s advice.
How can placenta praevia affect me and my baby?
There is a risk that you may have vaginal bleeding, particularly towards the end of your pregnancy. Bleeding from placenta praevia may be very heavy and can sometimes put mum and baby at risk.
How is a low-lying placenta diagnosed?
Your midwife or doctor will look at your placenta’s position at your 18 to 21 week ultrasound scan.
If your placenta is low, you’ll be offered an extra ultrasound scan later in your pregnancy (usually at about 32 weeks) to check its position again.
In 90% of cases, the placenta is no longer low-lying by this point.
Your midwife or doctor may think you have placenta praevia if:
- you have bleeding during the second or third trimester – this is usually painless and may happen after sex
- if the baby is lying in an unusual position, for example bottom first (breech) or lying across the womb (transverse)
If you have any bleeding during pregnancy, with or without pain, you should always get checked out straight away. If you’re in your first trimester, contact your doctor, midwife or Early Pregnancy Unit. If you are more than 12 weeks pregnant, go to your local A&E or contact your hospital maternity unit immediately.
You may be advised to avoid having sex (including the use of penetrative sex toys) for the rest of your pregnancy.
What treatment will I have?
If your placenta is low-lying at your 20-week scan, you’ll be offered another ultrasound scan at around 32 weeks. This may include a transvaginal ultrasound scan, which is when a probe is gently placed inside the vagina to check exactly where your placenta is lying. Don’t worry, this is safe for you and your baby.
The length of your cervix may also be measured at your 32-week scan to predict whether you may go into labour early and whether you are at increased risk of bleeding.
If the placenta hasn’t moved up, you should be offered another ultrasound scan at 36 weeks. The results of this scan will help you and your doctor plan the safest way for you to give birth.
If you have placental praevia, there is a risk you may give birth prematurely. So you may be offered a course of steroid injections between 34 and 36 weeks of pregnancy to help your baby’s lungs to become more mature.
If you do go into labour early, you may be offered medication to try to stop your contractions. This will give you time to have a course of steroid injections. If you have severe bleeding or progressing labour your baby may need to be delivered.
If you have vaginal bleeding, you may need to be admitted to hospital. This is because there is a small risk that you could bleed suddenly and heavily. If this happens, you may need an emergency caesarean section.
What do I need to do if I have a low-lying placenta?
When to contact the hospital
If you know you have a low-lying placenta, you should contact the hospital immediately if you have:
- vaginal bleeding, including spotting
- pain, including any vague, period-like aches.
- If you have any bleeding, your doctor may need to do an internal examination to check where it’s coming from. This is safe and they will ask for your permission before they start.
Anaemia is a blood condition that develops when you don’t have enough red blood cells. Red blood cells contain haemoglobin, a protein that carries oxygen around your body and to your baby.
If you have a low-lying placenta, it’s important to try to avoid developing anaemia, which can be common in pregnancy. Eating a healthy, balanced diet will help you either prevent or manage anaemia. Iron supplements may also help, if your healthcare team recommends them.
How will my baby be born?
Your healthcare team will talk to you about what your options are for giving birth.
You may be advised to give birth early if you have any heavy bleeding before your due date.
If the edge of your placenta is very close (less than 2cm) to your cervix (entrance to the womb), the safest way to give birth is by caesarean section. This will usually be between 36 and 37 weeks. But if you have had vaginal bleeding during your pregnancy, you may be advised to have your caesarean earlier than this.
If the placenta is further than 2cm from your cervix, you may be able to have a vaginal birth if you want one.
If you are having a caesarean section, a senior obstetrician (a doctor who specialises in pregnancy) will be there. This is because you may have heavy bleeding during the surgery. If this happens, you may need a blood transfusion. This is more likely if you have placenta praevia.
Talk to your doctor before your surgery if, for any reason, you do not want a blood transfusion.
Unfortunately, complications are more common in caesarean sections if you have a low-lying placenta. Your doctor should talk to you about the risks of major bleeding and hysterectomy (removal of the womb) before your caesarean. For most women, the risk of hysterectomy is low and will only occur as a last resort if other measures to control bleeding are not effective.
If you have placenta praevia:
you are at higher risk of having your baby early (less than 37 weeks).
your baby will need to be born by caesarean section because the placenta is blocking the birth canal.
Last revised: January 2021