Low Lying Placenta at 20 Weeks
This information leaflet has been given to you because you have been found to have a low lying placenta or a placenta covering your cervix at your 18-20+6 week fetal anomaly scan.
What is a low lying placenta?
The placenta is an organ that develops inside the uterus (womb) alongside the baby. It provides the baby with oxygen and nourishment from the mother’s blood system to keep it alive and help it grow. The placenta is also known as the ‘afterbirth’ and is delivered after the baby has been born.
When you attend for your 18-20+6 week fetal anomaly scan, the position of your placenta inside your uterus is also assessed. For some women the placenta may be located close to the cervix (the neck of your womb). This is known as a low lying placenta. When the placenta covers the inside opening of the cervix, this is referred to as placenta praevia.
For most women, as the uterus grows throughout their pregnancy, the placenta moves up and away from the cervix allowing room for the baby to be born vaginally. However, for some women the placenta remains close to or covering the cervix meaning a vaginal (natural) birth is not possible.
What happens next?
For most women with a low placenta at their routine anomaly scan, their placenta will move far enough away from their cervix allowing the possibility of a vaginal birth.
If your placenta is close to, but not covering your cervix (low placenta), your sonographer will arrange for you to have another scan at 36 weeks to assess whether your placenta has grown far enough away from your cervix to allow for a vaginal birth.
If your placenta is covering the cervix (placenta praevia), your sonographer will arrange with you to have a follow up scan at 32 weeks. If the placenta is still covering your cervix at this stage, another scan at 36 weeks will be arranged and you may be referred to a consultant obstetrician by your midwife.
If your placenta is positioned low on the anterior wall (top or front wall) of your uterus and you have had a caesarean section previously, the sonographer will arrange a scan between 26 and 32 weeks, to further assess the placenta and cervix. If at this stage your placenta is still low or covering the cervix, a further scan will be performed at 36 weeks gestation to re-assess.
A transvaginal scan may be necessary to achieve the best views of your placenta and cervix. This involves inserting a small sterile ultrasound probe into your vagina. It sits at the level a tampon would sit and does not touch your cervix or uterus. This should not hurt, and is completely safe in pregnancy. A chaperone will be present if this needs to be performed.
Only 1 in 200 pregnant women at full term (37-40 weeks pregnant) will have a placenta that remains low or covering the cervix (placenta praevia) and be unable to have a vaginal birth for this reason.
Is there anything I should be aware of?
Some women with a low placenta or a placenta praevia experience bleeding during their pregnancy. If this happens to you it is important for you to contact the Maternity Unit. You will be asked to come into hospital (maternity) to be reviewed by a midwife and obstetrician.
Although it is unlikely, if you do experience any pain, or think you are going into premature labour, and have been told your placenta is low or covering your cervix, it is important for you to contact the Maternity Unit immediately as you will need to be assessed by a midwife and doctor.
It is important that you inform any healthcare professional or alternative therapist you receive care from during your pregnancy that your placenta is low as the care they give you may change.
If your placenta is covering your cervix (placenta praevia), your obstetrician or midwife may advise you to not have sexual intercourse.
Contact numbers
We hope that you have found this information useful. If you have any questions or are worried about anything, please call and speak with your midwife.
Maternity Unit: 01305 254252
About this leaflet
Authors: Clementina Bailey, Midwife Sonographer
Written July 2022
Approved: May 2025
Review date: May 2028
Edition: v2