Low lying placenta, placenta praevia and placenta accreta after 32 weeks

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You have been given this leaflet as you have been found to have a low lying placenta at your ultrasound scan. If you have any further questions about this, you can ask your midwife, or obstetrician.

The Placenta

The placenta develops together with the baby in your uterus during pregnancy. It attaches to the wall of your uterus and provides a connection between you and your baby. Oxygen and nutrients pass from your blood through the placenta into your baby’s blood. The placenta is delivered shortly after the baby is born and it is sometimes called the afterbirth.

What is a low lying placenta?

In some pregnancies, the placenta attaches low down in the uterus. A placenta is termed ‘low lying’ if it is closer than 20mm to your cervix (the neck of the womb) at the 20 week scan. An uncomplicated low-lying placenta will likely move upwards (in 90% of cases) as the pregnancy progresses.

What is placenta preavia?

Placenta Praevia is when the placenta is low down and covering the cervix (neck of the womb). Placenta praevia is more common if you have had one or more previous caesarean births, if you had had fertility treatment in order to fall pregnant, or if you smoke.

What does having a low lying placenta mean?

Only 1: 200 people overall will have a placenta praevia at the end of their pregnancy. If the placenta has moved clear of the cervix, you will not need any further review. If you are found to have a low lying placenta, or a placenta praevia at the 20-week scan, you will be referred for a repeat scan at 32-weeks of pregnancy to check if it has moved upwards. This sometimes involves doing an internal (transvaginal probe) ultrasound scan.

What happens if the placenta is still low lying after the 32 week scan?

If the placenta remains low at the 32-weeks scan then you will be referred to see an obstetrician to discuss on-going management If the placenta remains low lying, an additional scan will be performed at 36 wks.

If the placenta remains low lying or there is a placenta praevia, a caesarean delivery is advised as the placenta blocks the baby’s way out. Additional care, including whether or not you need to be admitted to hospital, will be based on your individual circumstances.

What are the risks for me and my baby?

There is a risk that you may experience vaginal bleeding, particularly towards the end of the pregnancy, because the placenta is low down in your uterus. Bleeding from placenta praevia can be very heavy, sometimes putting both you and your baby’s life at risk. If you know you have a low-lying placenta, you should contact the hospital straight away if you have any vaginal bleeding, contractions or pain.

How will my baby be born?

Towards the end of your pregnancy, if placenta praevia is confirmed, you will have the opportunity to discuss your birthing options with your healthcare team according to your own individual circumstances. If the edge of your placenta is less than 20 mm from the entrance to the cervix on your scan at 36 weeks, a caesarean will be the safest way for you to give birth. If the placenta is further than 20 mm from your cervix you can choose to have a vaginal birth. If you do not experience bleeding in the pregnancy, your caesarean will usually take place between 36 and 37 weeks.

If you have had vaginal bleeding during your pregnancy, your caesarean may need to take place earlier than this. If you have heavy bleeding before your planned date of delivery, you may be advised to have your baby earlier than expected During your caesarean, you may have heavier than average bleeding. There are many different things that your doctors can do to stop the bleeding and these will be discussed with you.

What is placenta accreta?

Placenta accreta is a rare (between 1 in 300 and 1 in 2000) complication of pregnancy. This is when the placenta grows into the muscle of the uterus, making delivery of the placenta at the time of birth very difficult. Placenta accreta is more common in women with placenta praevia who have previously had one or more caesarean births, but it can also occur if you have had other surgery to your uterus, or if you have a uterine abnormality such as fibroids or a bicornuate uterus. It is more common if you are older (over 35 years old) or if you have had fertility treatment, especially in vitro fertilisation (IVF).If placenta accreta is suspected during your ultrasound scans, additional tests such as magnetic resonance imaging (MRI) scans may help with the diagnosis.
If placenta accreta is suspected before your baby is born, your doctor will discuss your options and the extra care that you will need at the time of birth. It may be planned for you to have your baby early, between 35 and 37 weeks of pregnancy, depending on your individual circumstances.

Contacts

Further information

Royal College of Obstetrics and Gynaecologists