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Fetal anatomy scan

Pregnant women should be offered an anatomy exam as part of standard antenatal care.

You will usually have this at 18 to 22 weeks. It is also called an 'anomaly scan'.

Anatomy scans can tell you:

  • how your baby is developing
  • if your baby has birth defects like spina bifida and heart problems
  • the sex of your baby - scans can sometimes get this wrong, or it may not be possible to tell depending on how your baby is lying in the womb
  • the position of the placenta

Most scans will show you that your baby is developing normally.

Scan results

Sometimes babies can have health problems while they are developing in your womb. An anatomy scan will detect many of these problems.

This allows you and your midwife or obstetrician to make plans for the birth and for any aftercare you and your baby may need.

If they identify a problem, they will offer you an appointment with a fetal medicine specialist.

The scan will not detect all health issues. No test is fully accurate. Some health issues do not show up on the anatomy scan.

These include:

  • some cases of Down syndrome
  • some cases of cerebral palsy
  • autism

If the scan shows that your baby is growing too quickly or too slowly, you may be offered extra scans to check their growth.

You may be offered a scan to check the placenta at 32 to 34 weeks. This is to rule out placenta praevia (low-lying placenta)

Sometimes you will be recommended to have tests like amniocentesis or CVS sampling to confirm a diagnosis.

Baby's sex

Sometimes the person doing the scan may not be able to see parts of your baby’s body. For example, they may not be able to see the genitals to determine your baby's sex.

If you do not wish to know the sex of your baby during the scan, tell the person doing the scan.

Bringing someone with you

An ultrasound scan can be a happy event. But sometimes they can detect that your baby is unwell. Or you might get unexpected news, such as there is more than 1 baby.

Check with your maternity unit if you may bring someone with you for support.


Let the person doing the scan know if you had a previous complicated pregnancy.

Contact the ultrasound department before your appointment if you feel you may need extra support during the scan.

Page last reviewed: 12 June 2023
Next review due: 12 June 2026

This project has received funding from the Government of Ireland’s Sláintecare Integration Fund 2019 under Grant Agreement Number 123.