Dating scan

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What is the dating scan?

The dating scan is used for people who do not wish to have screening for Down’s, Edwards or Patau’s syndrome, or who are thought to be more than 14 weeks into their pregnancy. This scan is used to calculate the gestation of the baby so we can plan your antenatal care. Usually you would have this scan before 14 weeks; however, sometimes it is required later if this is your first pregnancy scan.

This scan takes 15 to 20 minutes.

What happens before my examination?

Please come with a full bladder.

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 measure the crown rump length (CRL). This measures the length of your baby from head to bottom and is used to date the pregnancy. This can be used to calculate estimated date of delivery (EDD). However, if this date is less than 10 weeks, you will be entitled to another scan at 12 weeks.

If your pregnancy is more than 14 weeks, the head circumference will be measured to calculate your EDD.

We will also assess other parts of your baby’s body, including the head, brain, abdomen, arms and legs.

If your baby is not in a very easy position for the sonographer to see, you may be asked to wriggle your hips, jump up and down or walk around outside.

What happens after?

The sonographer will explain the results of your scan and a copy will be given to you. If you do not understand the results please ask the sonographer to explain.

We will arrange for any subsequent scans at the correct time.