Mid pregnancy scan

The purpose of the mid-pregnancy scan (sometimes known as a fetal anomaly scan) is to check your baby's health and development.

It's offered between 18 and 21 weeks of pregnancy.

What the scan can show

The mid-pregnancy screening scan is used to look at your baby's health and development, including the development of their:

  • brain
  • spinal cord
  • heart
  • bowel
  • kidneys
  • arms and legs

If the scan shows your baby may have a health condition or chromosomal condition, your healthcare professional will discuss it with you at the time.

Ask your midwife if you would like to know full details of the scan's findings.

How accurate is the scan?

Sometimes the sonographer isn't able to get a clear view because of:

  • your baby's position or age
  • the amount of amniotic fluid surrounding your baby
  • your own bodyweight
  • scar tissue left by an abdominal operation, such as a previous Caesarean section

Scans aren’t as reliable at detecting some conditions which:

  • don't affect the appearance of your baby
  • develop later in pregnancy
  • affect your baby’s heart
  • develop after 21 weeks

Although the sonographer and doctors can usually be confident in the findings, no screening test will detect all cases. This means that in a small number of cases, babies are born with health conditions or chromosomal conditions that haven't been picked up through the scan.

If the scan is inconclusive

Most people find that their baby's developing well. Some conditions may not be picked up by the mid-pregnancy scan.

If the sonographer thinks there could be an issue, they may ask for a second opinion from another healthcare professional. If this happens they’ll tell you what they’re checking for, but they might not be sure yet.

If the sonographer finds something that means there’s a higher chance of your baby having a chromosomal condition, you may be offered a diagnostic test.

Pre-natal support and treatment planning

Finding out about health conditions or chromosomal conditions before birth can help parents get support earlier and make decisions for themselves and their baby. For example, you may want to prepare and plan treatment for after your baby's born.

If your baby may need an operation soon after birth (such as repairing a tummy hernia) it can be arranged for you to deliver your baby in a hospital where this can be done within the first few hours.

Will I need another scan?

You might need another scan if:

  • you take some types of medication
  • you have a long-term medical condition
  • the sonographer isn't able to see everything clearly

If the sonographer hasn't been able to see your baby clearly you may be asked to come back on another day for a repeat scan.

If no issues are found during the mid-pregnancy screening scan, you probably won't need another scan during your pregnancy.

Last updated:
14 March 2022

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