Guidance

Screening in pregnancy: 20-week screening scan

Updated 31 October 2021

Applies to England

Public Health England (PHE) created this information on behalf of the NHS. In this information, the word ‘we’ refers to the NHS service that provides screening.

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Purpose of the 20-week screening scan

This scan is a screening test that takes place between 18 weeks and 20 weeks plus 6 days of pregnancy.

The scan looks for 11 physical conditions in your baby. It cannot find every condition.

To check for the 11 conditions, the scan looks in detail at your baby’s:

• abdomen (tummy)
• bones
• brain
• face
• heart
• kidneys
• spinal cord

Most scans are carried out by specially trained staff called sonographers.

Screening for 11 physical conditions

Screening is your choice. You do not have to have the scan. Some people want to find out if their baby has one of the 11 physical conditions and some do not.

If you choose to have this scan, you may need to make important personal decisions based on the results. Whatever you decide, you will be supported by your healthcare team.

If you choose not to have the scan you can still have all other parts of your usual antenatal care.

Please let your midwife know if you want more information about whether or not to have screening.

Safety of the scan

There are no known risks to you or your baby from having an ultrasound scan. It is important to think carefully if you want to have the scan or not.

The scan

To get clear views of your baby, the scan is performed in a dimly lit room and the sonographer might need to keep the screen directly facing them or at an angle.

You might need to have a full bladder when you come for the appointment. This should be made clear when making your appointment. If you are not sure, you can contact the hospital.

Having the scan does not hurt, but the sonographer might need to apply slight pressure to get clear views of your baby. This might be uncomfortable. A black and white picture of your baby will then be seen on the ultrasound screen.

The appointment usually takes around 30 minutes.

1. You will be asked to lie on a couch.
2. You will be asked to raise your top to your chest and lower your skirt or trousers to your hips.
3. Tissue paper is tucked into your clothing to protect it from the ultrasound gel. The gel is put on your tummy. The gel may be cold.
4. The sonographer moves a hand-held device called a probe over your tummy to carefully examine your baby’s body. The gel makes sure there is good contact between the probe and your skin.

The sonographer may be quiet during the scan. It is important for them to be able to concentrate so they can perform a good quality scan.

You may like someone to come with you to the scan. Most hospitals do not allow children to attend scans. Please ask your hospital about this before your appointment.

Possible results of this scan

In most cases, the scan will show that your baby appears to be developing as expected and does not have any of the 11 physical conditions screened for.

You will always be told if anything unexpected is found during your scan.

During your scan the sonographer might ask for a second opinion from another member of staff.

Sometimes it is difficult to get a clear view of your baby. This might be because your baby is lying in an awkward position or you are above average weight. This does not mean there is anything to worry about.

In this case, you will be offered a second scan by 23 weeks of pregnancy. The sonographer will try to complete the scan at this next appointment, but it is not always possible.

Very occasionally this second scan cannot be completed. In this case, you will not be offered another screening scan, but you will be offered an all-over physical examination for your baby after birth.

The sonographer will be able to tell you the findings at the time of your scan.

Scans cannot find all conditions. There is always a chance that a baby may be born with a condition that could not be seen on scan.

Your personal information

The NHS Screening Programmes use personal information from your NHS records to invite you for screening at the right time. Public Health England also uses your information to ensure you receive high quality care and to improve the screening programmes. Find out more about how your information is used and protected, and your options.