Anomaly scan

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What is a 20 week Anomaly Scan?

This scan is a screening test used to check for physical abnormalities and to assess your baby for 11 different conditions that may be detected before birth. All these checks are part of a national screening programme for pregnancies.

This scan takes up to 30 minutes, sometimes longer if the baby is in a difficult position.

What happens before my examination?

Please make sure your bladder is empty before you have your Anomaly scan.

Please note we are a university trust and regularly have trainee sonographer and student midwives present at the scan. If you do not wish for a student to be present please inform the sonographer.

What will happen during the examination?

The sonographer will perform a series of measurements to check the growth of the baby. These are:

• HC: Head circumference (around the baby’s head) and structures inside brain (Vp: ventricle and TCD: cerebellum).

• AC: Abdominal circumference (around the baby’s waist line).

• FL: Femur length (the length of the thigh bone).

Other areas examined are:

• Fetal brain.
• Spine.
• Heart.
• Stomach.
• Kidneys.
• Bladder.
• Limbs (we do not count the number of fingers and toes).
• Face.
• Placenta position and liquor (fluid around the baby).

We examine the structures to see if they are developing as we’d expect to see for this stage of the pregnancy. However, not all abnormalities can be detected.

If your baby is not in a very easy position for the sonographer to see, or you have a high Body Mass Index, you may be asked to wriggle your hips, jump up and down or walk around outside. Sometimes if the baby stays in the same position despite trying these things, we will ask you to come back on a different day, usually within two weeks.

Some people may require growth scans later in the pregnancy and an additional check on their placenta. If these are need they are requested by your consultant obstetrician.

Will I find out the sex of my baby?

If you want to know the sex of the baby, please inform the sonographer at the beginning of the scan. If it is possible to see the sonographer will inform you at the end of the scan, after the checks on the baby’s well being are finished.

What happens after?

The sonographer will explain the results of the scan and a copy will be given to you or transferred onto your digital maternity notes. If there have been any unexpected findings identified you will be referred to a fetal medicine consultant for confirmation or second opinion and further tests. You will be able to speak to a screening midwife for support. If you do not understand the results please ask the sonographer to explain.

For more detailed information, you can access the Fetal Anomaly Screening Programme (FASP) information at: FASP: parent information on screening for conditions: GOV.UK