Low-Lying Placenta and Placenta Praevia: A Comprehensive Guide

What are Low-Lying Placenta and Placenta Praevia?

The placenta can develop in different parts of the uterus. In most pregnancies, it attaches to the sides or top of the womb. However, in some cases, it attaches lower down and may cover some or all of the cervix (entrance to the uterus).

• Low-Lying Placenta
  When the edge of the placenta is less than 2 cm from the cervix.
• Placenta Praevia
  When the placenta completely covers the cervix.

You will first find out about the location of your placenta during your mid-pregnancy ultrasound scan (anatomy scan) typically conducted between 18 and 21 weeks.
Having a low-lying placenta does not usually cause pain during pregnancy. It can be posterior (towards your back and low) or anterior (towards your front and low).

Are Low-Lying Placenta or Placenta Praevia common?

It is quite common to have a low-lying placenta at 20 weeks. In most cases, it resolves itself as the uterus grows. Only 1 in 200 people will still have a low-lying placenta or placenta praevia at the end of their pregnancy. The likelihood of having a low-lying placenta or placenta praevia is higher if you have had a previous caesarean section.

Who is at Risk of Placenta Praevia?

Placenta praevia is more likely if you:

• Smoke cigarettes or use cocaine.
• Have had fertility treatment, such as IVF.
• Have had one or more caesarean sections.
• Have had previous miscarriages or termination of pregnancy.
• Are aged 40 or older.

Can Placenta Praevia be prevented?

There is no specific way to prevent placenta praevia. While certain factors are linked to placenta praevia, they are not definitive causes.

Quitting smoking and avoiding cocaine can improve overall pregnancy health.

Symptoms and Diagnosis

How will I know if I have a Low-Lying Placenta?

Placenta praevia is usually detected during the mid-pregnancy ultrasound scan (18-21 weeks). If your placenta is low at that scan, you will be offered another scan at around 32 weeks to check its position.

Your midwife or doctor may suspect placenta praevia if you:

• Experience bleeding during the second or third trimester (usually painless and may happen after sex).
• The baby is lying in an unusual position (e.g. breech or transverse).

If you have any bleeding during pregnancy, with or without pain, contact your doctor, midwife, or Maternity Assessment Unit immediately.

How can a Low-Lying Placenta or Placenta Praevia affect me and my baby?

Vaginal Bleeding

There is a risk of vaginal bleeding, especially after sex or towards the end of your pregnancy, which can be very heavy.

Preterm Birth

There is a chance your baby may be born prematurely (before 37 weeks).

Caesarean Section

If the placenta is very close to or covering the cervix, a caesarean section is the safest way to deliver your baby.

What activities should I avoid?

What precautions should I take if I have a Low-Lying Placenta or Placenta Praevia?

Monitor for bleeding

Contact the Maternity Assessment Centre immediately if you have vaginal bleeding, contractions, or pain (including period-like aches).

Avoid heavy lifting

Take it easy and avoid activities that may strain your abdomen.

Sexual intercourse

• Penetrative sex may cause bleeding because the placenta is close to the cervix.
• Many women choose to avoid intercourse to reduce the risk of bleeding.
• If you have had previous bleeding episodes, it is recommended to avoid intercourse.
• If you have not had bleeding and the placenta is only slightly low, sex may be considered safe. However, if bleeding occurs, stop immediately and seek medical attention.

Flying and Travel

• The Royal College of Obstetricians and Gynaecologists (RCOG), does not explicitly prohibit flying with a low-lying placenta but advises caution.
• If you have placenta praevia or have had bleeding, you are at higher risk of sudden bleeding, which may be difficult to manage during travel.
• Airlines have different policies, but most require a “fit to fly” letter after 28-32 weeks and restrict travel after 36 weeks (or earlier if complications arise).
• If travel is necessary, discuss your plans with your doctor to ensure safe care is available at your destination.

What treatment will I have for Placenta Praevia?

Extra Scans

If your placenta is low-lying at 18-20 weeks, you will be offered another scan at around 32 weeks, which may include a transvaginal ultrasound scan to check the placenta’s exact position. If still low-lying at 32 weeks, you will have another scan at 36 weeks.

Extra antenatal care

No Immediate Concerns

If you are considered low-risk, with no history of caesarean sections and have a low-lying placenta at your anatomy scan you do not need to be seen by the Antenatal Clinic immediately. Our advice is to follow precautionary measures and report any vaginal bleeding to the Maternity Assessment Centre.

Follow-Up Scans

A scan at 32 weeks is necessary. If your placenta is still low-lying, schedule an appointment with the Antenatal Clinic. If the placenta moves and there are no risk factors, no appointment in the Antenatal clinic is needed.

When you have had a previous caesarean section

If you have had a caesarean section in the past and your placenta is found to be low lying and anterior at your anatomy scan, you will be referred to the Placenta Clinic to look for signs of Placenta Accreta Spectrum. This scan needs to be carried out between 20-26 weeks so that there is time to plan the best care for you and your baby if you are found to have this condition. Placenta accreta spectrum is a group of conditions where the placenta is attached to the uterus in an unusual way, most commonly to the previous caesarean section scar, and it may not be possible to remove it easily at the time of delivery.

The sonographer will make this referral after your scan if required and will let you know that they are doing so.

Giving birth with Placenta Praevia or Low-Lying Placenta

Mode and timing of delivery

Caesarean section

If the placenta is completely or partially covering the cervix (placenta praevia), a planned caesarean section will be recommended. Consultant obstetricians at LTHT recommend delivery by 39+0 weeks, but some women with a low-lying placenta may be advised to wait until 38 weeks or later, depending on individual circumstances.

During the caesarean section, a senior obstetrician (a doctor who specialises in pregnancy care) will be present due to the risk of heavy bleeding. If heavy bleeding happens, you may be offered a blood transfusion. This risk is higher with placenta praevia than with a low-lying placenta. If you are likely to refuse a blood transfusion, please inform your healthcare team as soon as possible.

Complications are more common in caesarean sections where the placenta is low-lying or in placenta praevia. Your doctor should discuss the risks of bleeding and the possibility of a hysterectomy (removal of the womb) to control heavy bleeding. The risk of hysterectomy is low and is usually considered only as a last resort, if other measures to control bleeding do not work.

Vaginal birth

If your placenta has moved at least 20mm from the cervix, a vaginal birth is usually safe.

If the placenta is 10-19mm away, a vaginal birth may be an option on a case-by-case basis, particularly if labour starts naturally and there has been no bleeding.

Other Considerations

Mental Wellbeing

Finding out you have a complication in pregnancy can be stressful. Talk to your midwife or doctor about your feelings. Support is available through your healthcare team.

Contact us

Please call the Maternity Assessment Centre immediately if you experience any vaginal bleeding:

Further information

Sources and Acknowledgements

This information has been developed based on guidelines from the Royal College of Obstetricians and Gynaecologists (RCOG), the Leeds Teaching Hospital Trust Obstetric Ultrasound Protocol.