Placenta praevia (low-lying placenta)

This leaflet contains information that you may find helpful if you have been told that you have or may have a low-lying placenta, also known as placenta praevia.

It may also be useful if you are a partner, relative or friend of someone in this situation.

Key Points:

• Placenta praevia is when the placenta attaches to the lower part of your uterus (womb) and is less than 20mm away from the cervix (neck of the womb).
• Sometimes the placenta can end up covering the cervix itself.
• Placenta praevia can cause heavy bleeding during pregnancy or at the time of birth

If you experience any bleeding during pregnancy, with or without pain, you should get it checked immediately. You should contact the maternity assessment line on 01223 217217 so that they can arrange to see you.

Placenta praevia

Placenta praevia occurs when the placenta attaches to the lower part of your uterus and is less than 20mm away from the cervix. Placenta praevia affects 1 in every 200 pregnancies.

As your pregnancy progresses, your uterus will grow which affects the position of the placenta. The placenta usually moves up and away from the cervix when this happens. If the part of your uterus that the placenta is attached to does not move up and away from the cervix, your placenta may still be low-lying at the late stages of pregnancy.

Having placenta praevia increases your risk of vaginal bleeding, particularly towards the end of your pregnancy. This bleeding can be heavy and could put you or your baby at risk.

Why do I have a placenta praevia?

Generally, we do not know why people have placenta praevia. However, we do know of some factors that make it more likely.

Placenta praevia has been associated with:

• Smoking
• Fertility treatment to get pregnant (including in vitro fertilisation (IVF))
• Have had 1 or more previous caesarean births
• Age 40 or older
• Multiple pregnancy (twins, triplets or more)
• Previous surgery on the uterus
• Endometriosis

Unfortunately, there is nothing that you can do to try to help move the placenta up and away from the cervix. But keeping in touch with your healthcare team and attending all your scheduled appointments will help to ensure that you and your baby are kept as safe as possible during your pregnancy and birth.

How is a placenta praevia diagnosed?

The position of the placenta is checked at your 18-to-21-week ultrasound scan. If your placenta is significantly low, you will be recommended a transvaginal (internal) ultrasound scan to confirm this. This scan is safe for both you and your baby.

Depending on how low your placenta is, you will be offered one of the following:

• If your placenta is low, but not covering the cervix, you will be offered an additional ultrasound scan at 36 weeks.
• If you placenta is low and covering the cervix, you will be offered an additional ultrasound scan at 32 weeks. If the placenta remains low at 32 weeks, you will be offered a further additional ultrasound scan at 36 weeks.
• If you have had a previous caesarean section: if you have a placenta praevia which is on the front wall of the uterus, you will be offered a referral to our fetal medicine team for further assessment of the placenta.

Your midwife or doctor may suspect you have a placenta praevia if:

• You experience any bleeding during the second or third trimester – this is usually painless and can occur after sex
• The baby is lying in an unusual position (e.g. lying across the uterus, known as a transverse presentation)

How does this change my pregnancy?

If you have been diagnosed with placenta praevia, you will be offered some extra treatment as part of your antenatal care.

Extra scans will be offered during your pregnancy to check whether the placenta has moved up and away, as mentioned previously.

If you have experienced bleeding in your pregnancy due to placenta praevia, there is an increased chance your baby may be born preterm (before 37 weeks). If there is a high chance your baby may be born early, you may be recommended a course of steroid injections (2 injections, 12 to 24 hours apart) which help to mature your baby’s lungs. Please see the antenatal corticosteroids information leaflet on the Rosie website.

How will my baby be born?

When a diagnosis of placenta praevia is confirmed, your healthcare team will discuss the safest way for you to give birth, considering both your preferences and your individual circumstances.

If your placenta is less than 20mm from the entrance to the cervix or is covering the cervix at your 36-week scan, a caesarean birth is recommended as the safest way for you to give birth. A vaginal birth is not considered safe because the placenta can obstruct the birth of the baby. Additionally, as the cervix dilates the placenta can become detached before the birth of the baby, causing major blood loss which puts you and your baby at risk.

A caesarean birth may be offered after 36 weeks, with the actual timing agreed with full discussion considering your individual factors and preferences. If you have been experiencing bleeding during your pregnancy due to placenta praevia, you may be advised to have your caesarean birth earlier than this.

If your placenta is further than 20mm from your cervix, both vaginal birth and planned caesarean birth are considered safe options.

If you are having a caesarean birth, a senior obstetrician and an anaesthetist will be present at the time of birth.

Complications are more common in caesarean births if you have placenta praevia. Your doctor will talk to you about the risk of major bleeding and hysterectomy (removal of the womb) before your caesarean birth. For most people, the risk of needing a hysterectomy is low and will only occur if all other measures to control heavy bleeding are not effective.

If you have placenta praevia, you are more likely to need a blood transfusion, particularly if you are experiencing heavy bleeding. During your caesarean birth, blood will be available should you require a transfusion. If you feel that you cannot accept a blood transfusion under any circumstances, you should inform your healthcare team as early as possible in your pregnancy. This will give you and your healthcare team time to discuss alternative plans as necessary.

Contacts / further information

If you have any queries at any time, please discuss these with your doctor or midwife.

Early pregnancy unit - 01223 217636 (up to 13 weeks of pregnancy)

Maternity assessment Line - 01223 217217 (urgent questions, after first scan)

More information is also available from:

• NICE National Institute for Health and Care Excellence (opens in a new tab)
• Royal College of Obstetricians and Gynaecologists (opens in a new tab)

References / sources of evidence

• Placenta praevia, placenta accreta and vasa praevia (opens in a new tab)
• What complications can affect the placenta? (opens in a new tab)
• Low-lying placenta (placenta praevia) | Tommy's (opens in a new tab)