Anomaly scan

An anomaly scan takes a close look at your baby and your womb (uterus) at about 20 weeks of pregnancy. The person carrying out the scan (Sonographer) will check that your baby is developing normally.


  • Reassure you that your baby is developing normally.
  • Confirm the gestational age of your pregnancy.
  • Confirm the number of fetuses and, if twins, whether they are identical or not.
  • Detect birth defects, such as a Spina Bifida or heart problems.
  • If you are concerned about the chances of chromosome issues, this scan can search for subtle markers that may suggest a higher risk that your baby may have a syndrome.
  • If you want to know your baby’s gender this can usually be seen at this scan.
  • When you attend for this scan we will tell you about everything that we see, unless you advise us that there are certain things that you don’t want to know about, such as your baby’s gender or markers for chromosome issues.

This ultrasound scan is very accurate, but unfortunately it cannot diagnose 100% of congenital abnormalities. If the scan is complete, we would expect to pick up at least 95% of cases of Spina Bifida, 80% of cases of cleft lip or palate, and 60% to 70% of cases of congenital heart disease.

This scan can also identify 50% to 70% of cases of Down syndrome, but only an amniocentesis can give you this information for certain. It is also important to Realise that ultrasound scans in pregnancy do not detect problems like cerebral palsy or autism.

Sometimes babies with chromosomal abnormalities have signs called ultrasound markers. These include thick skin in the neck, excess fluid in the kidneys, short arms or legs, white spots in the baby’s heart or abdomen, or choroid plexus cysts in the brain.

While some babies with chromosomal abnormalities have these markers, it is important to remember that many normal babies also have these signs. If the scan suggests a problem, you will be told this immediately. You will be able to discuss the findings immediately with a consultant who Specialises in fetal medicine.

The only way to diagnose or exclude a chromosomal problem for certain is to have an amniocentesis. If you would prefer not to know about these markers, please inform us prior to the scan.

A full support service will be available for you should any issue be detected, including a referral to an appropriate pediatrician. A copy of your report will be sent to your referring hospital, doctor or midwife to ensure good communication.

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