How does anomaly scan work?

A sonographer moves a handheld probe over your abdomen using gel to help sound waves travel. The images are displayed on a monitor while the sonographer checks structures such as the brain, spine, heart, face, abdomen, kidneys and limbs. They also assess the placenta, umbilical cord and amniotic fluid, and take measurements to compare with expected growth.

The scan is also called a 20-week scan or mid-trimester scan. It is a screening examination, so it can identify features that need further assessment but cannot detect every condition or predict a child’s future health.

Wear clothing that allows access to your abdomen and follow the clinic’s instructions about eating, drinking or bladder preparation. The appointment usually involves lying back or slightly tilted while images are taken. You may feel pressure from the probe, and you might be asked to change position so the baby moves into a clearer view.

If the view is limited, the sonographer may need extra time or arrange another scan. You can ask whether you may bring a support person and when results will be discussed. For background on the examination, see [Anomaly Scan](/treatments/pregnancy-and-birth-care/anomaly-scan/).

Contact your maternity team promptly for bleeding, severe abdominal pain, fluid leaking, regular painful contractions or a marked reduction in your baby’s movements after you have started feeling a pattern. These symptoms need clinical assessment and are not determined by the scan result.

If the scan identifies a possible concern, your maternity team may explain the finding and offer a repeat scan, specialist imaging or other tests. A possible neural finding does not by itself confirm Neural Tube Defects.

Ask which organs and pregnancy measurements will be reviewed, whether the placenta position needs follow-up, how you will receive the result, and what happens if the images are incomplete. You can also ask whether 3D/4D Ultrasound adds anything useful for your specific appointment and how this scan differs from a Nuchal Translucency Scan.