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Anomaly Scan (20 week scan)

Information for pregnant women who are referred for an Anomoly scan.

Purpose of the Anomaly Scan

The anomaly scan is commonly referred to as the ’20 week scan’. It can take place between 18 and 22+6 weeks of pregnancy but is usually arranged at approximately 20+6 weeks gestation. The scan itself lasts approximately 30 minutes. Ultrasound waves are used to carry out the scan and there are no known risks to you or the baby. The scan is primarily to screen for 11 different conditions with your baby but cannot detect everything. 

Preparing for your Anomaly Scan

We ask you to come for your anomaly scan with a full bladder. You should drink a pint of water approximately an hour before your appointment time.

Please also remove any belly button bars or rings as these may damage the ultrasound equipment.

You may bring a support person to the scan appointment who can come into the exam room with you. We ask you do not bring children to the hospital unless absolutely necessary. Your support person may be asked to wait outside with the child if this situation occurs. 

Performing the Anomaly Scan

The scan will be performed in a dimly lit room and you will be asked to lie on a flat couch. You will be asked to move your trousers or skirt down onto your hips and tissue will be tucked in to protect your clothes. Clear (perhaps cold) ultrasound gel will then be applied and the sonographer will commence the exam. 

To get optimum views of your baby, a slight pressure may have to be applied. The sonographer will be concentrating and usually quite quiet throughout. The exam usually takes the full 30 minutes as there is a vast amount of anatomy to image.  

To get good quality images it may be necessary for you to get up, move your hips or empty your bladder. In some cases you could be asked to go for a walk and return for a second attempt. 

During the Anomaly Scan

This scan is likely to be the lengthiest one you will have. During the scan these things will be looked at in detail and images taken:

  • Measurements of head, abdomen and femur (the bone of the thigh) length which generate an estimated fetal weight of your baby at that time
  • Baby’s brain, face, lips, nose, arms, hands, heart, diaphragm, stomach, cord insertion, kidneys, bladder, legs, feet and spine are observed (fingers and toes are not counted)
  • The position of your placenta is observed 
  • The amount of fluid around your baby is observed

This anatomy is observed to detect 11 physical conditions that are screened for at the anomaly scan. More information about these conditions can be found within the ‘Screening tests for you and your baby’ leaflet online or on your BadgerNotes app.  

As this is a screening exam it means these conditions are not always detected and the rate of detection varies between them. For example, Spina Bifida can usually be seen clearly on scan and 9 out of 10 (90%) are noted at this stage, however, other conditions such as heart defects are more difficult to see and about half (50%) will be detected. 

In most cases the scan will show your baby appears to be developing as expected and the sonographer will inform you of this at the end. If there are any abnormalities suspected this will also be explained and you will likely be referred to Fetal Medicine Department at the Royal Victoria Infirmary for another scan, a discussion of the findings and a diagnosis. 

The sonographer will also inform you of the position of your placenta and what this means for your pregnancy. 

Determining your baby’s sex

We do not routinely look however, if you wish to know, the sonographer will make every effort to determine which sex is favoured at the end of your scan appointment. On rare occasions, usually due to your baby’s position in the womb, it isn’t possible to see clearly and if this was the case you would be informed. Further, despite our best efforts at times we get the sex incorrect. 

Occasionally, women and their families like to have this information provided to them in a sealed envelope to allow them to find out in a different setting. We are happy to do this if you ask. It is worth noting, in this instance, the sex determined will also be recorded on your scan report published to your BadgerNotes but it will be up to you when you open it. 

Other things to note

No money is currently being taken for scan photos due to Covid 19, instead two scan photos will be printed for you for free. 

Video equipment is not to be used under any circumstances in the scan room. We ask that all phones are turned off for the duration of the exam. 

If when you are scanned your baby is in an awkward position or if your weight is slightly above average it may mean the scan cannot be completed in the first instance. If this is the case you will be offered another scan appointment at approximately 22+6 weeks of pregnancy to look at the remaining anatomy. Commonly, the baby’s heart is what you would be recalled to observe. This should not be cause for alarm and does not mean anything is wrong. 

Your baby’s health record or ‘red book’ will be supplied to you at this scan. It is important you keep it safe as it is required to record important information about your child until they start school. You do not have to bring it to antenatal appointments but you must bring it to your birth to document initial observations. 

Your scan report should be uploaded to your BadgerNotes a few hours after your appointment.

Useful sources of information 

  1. Gov – The 20 week screening scan
  2. Gov – Screening tests for you and your baby
  3. NHS – 20 week scan

Contact numbers

If you have additional queries, particularly regarding the appointment time please contact:

Women’s Health Clinic

Or any other pregnancy questions please contact:

Pregnancy Assessment Unit

24 hours 0191 445 3678

Data Protection

Any personal information is kept confidential.  There may be occasions where your information needs to be shared with other care professionals to ensure you receive the best care possible.

In order to assist us to improve the services available, your information may be used for clinical audit, research, teaching and anonymised for National NHS Reviews and Statistics.  

Further information is available via Gateshead Health NHS Foundation Trust website (https://www.gatesheadhealth.nhs.uk/fairprocessing) or by contacting the Data Protection Officer by telephone on 0191 445 8418 or by email [email protected].