Understanding scans

Understanding your scan

What do all those letters and measurements mean? A plain-English guide to your scan report and the questions worth asking.

When
Any scan
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Clinically reviewed by The Window to the Womb Clinical Governance Team ยท Last reviewed June 2026

Scan reports are full of abbreviations, and it's easy to feel lost. Here's what the common ones mean, and what to focus on.

Remember: measurements are compared against typical ranges, and a baby measuring a little ahead or behind is usually completely normal.

๐Ÿ”What it checks

  • CRL, crown-rump length, used to date early pregnancy
  • BPD & HC, head measurements
  • AC, abdominal circumference
  • FL, femur (thigh bone) length
  • EFW, estimated fetal weight (an estimate, with a margin)

๐Ÿ’›What to expect

If a measurement sits outside the usual range, your team may simply suggest another scan to keep an eye on things, it doesn't automatically mean there's a problem.

It's your scan and your baby: it's always okay to ask the sonographer to explain anything in plain language.

๐Ÿ’ฌQuestions worth asking

  • Are all the measurements within the expected range?
  • Is there anything you'd like to check again?
  • Can you explain that in everyday terms?
Good to know. This is general information, not a diagnosis. Your sonographer and midwife are the right people to interpret your individual results.
Sources: www.nhs.uk

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