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Dating Scan Complete Guide

The dating scan is your first routine NHS ultrasound and one of the most important appointments of your pregnancy. It confirms your due date, checks your baby's development, and screens for certain conditions. Here's your complete guide.

Table of Contents

  1. What Is the Dating Scan?
  2. When Is the Dating Scan?
  3. What Happens at the Dating Scan?
  4. What Do They Measure?
  5. Do You Need a Full Bladder?
  6. Can You Bring Someone?
  7. What Happens After the Scan?
  8. How to Prepare

What Is the Dating Scan?

The dating scan is an ultrasound scan offered to all pregnant women on the NHS between 11 and 14 weeks of pregnancy. Its primary purpose is to estimate your due date by measuring your baby from the crown (top of the head) to the rump (bottom). This measurement, called the crown-rump length (CRL), is most accurate in the first trimester.

As well as dating the pregnancy, the scan checks that your baby is developing as expected, confirms the heartbeat, and looks for any early signs of complications. If you choose to have combined screening for Down syndrome, Edwards syndrome, and Patau syndrome, the nuchal translucency (NT) measurement will be taken at this scan too.

When Is the Dating Scan?

The NHS offers the dating scan between 11+2 and 14+1 weeks of pregnancy. Your midwife will book it for you at your booking appointment, which usually happens between 8 and 12 weeks. The ideal timing is around 12 weeks, as the CRL measurement is most accurate then and the NT screening window is open.

If you're not sure of your dates — for example, if your periods are irregular — the dating scan is especially useful for pinpointing how far along you are.

What Happens at the Dating Scan?

You'll be asked to lie on a couch and lower your clothing to expose your lower abdomen. The sonographer will apply gel to your tummy and use a handheld probe to capture images of your baby. The gel can feel cold, but it's harmless and wipes off easily.

The scan typically takes 15 to 20 minutes, though it can take longer if your baby is in a tricky position or you need to wait for them to move. The sonographer may press the probe quite firmly to get a clear view — this can be a little uncomfortable but shouldn't be painful.

You'll usually be able to see your baby on the screen during the scan. Many hospitals let you bring your partner in to watch, and you can often buy a scan photo for a small fee.

What Do They Measure?

During the dating scan, the sonographer will:
  • Measure the crown-rump length (CRL) to estimate your due date. This is the most accurate way to date a pregnancy in the first trimester.
  • Check the heartbeat to confirm your baby is alive and developing.
  • Measure the nuchal translucency (NT) if you've chosen combined screening. This is a fluid-filled space at the back of your baby's neck.
  • Count the number of babies — yes, twins are sometimes discovered at this scan!
  • Check overall development, including the skull, spine, limbs, and stomach.

Do You Need a Full Bladder?

Most hospitals don't require a full bladder for a 12-week abdominal scan, because the baby is large enough to see clearly by this stage. However, some trusts do still ask you to drink water before your appointment, as a full bladder lifts the uterus and improves the view. Check your appointment letter for specific instructions — if in doubt, call the ultrasound department.

Can You Bring Someone?

Yes, most hospitals allow you to bring one person into the scan room, usually your partner. Some hospitals allow more than one, but policies vary widely. Children are sometimes permitted but not always — check with your hospital beforehand. It's best to ask when you receive your appointment so there are no surprises on the day.

What Happens After the Scan?

If everything looks healthy, you'll be given your estimated due date and sent on your way. Your midwife will discuss the results at your next appointment. If the NT measurement is raised or there are any concerns, you'll be offered further tests such as NIPT, CVS, or amniocentesis. The sonographer or your midwife will explain your options without pressure.

How to Prepare

- Wear loose, two-piece clothing for easy access to your tummy. - Check your appointment letter for bladder instructions. - Bring your maternity notes if you have them. - Write down any questions you have. - Arrive 10-15 minutes early to fill in any paperwork.

Frequently Asked Questions

### How accurate is the dating scan?

The dating scan is the most accurate way to estimate your due date, with an accuracy of around 5 to 7 days in the first trimester. Once your due date is set at this scan, it usually isn't changed even if later scans give a slightly different measurement.

Can the dating scan tell the gender?

NHS sonographers don't assess gender at the dating scan. At 12 weeks, external genitalia aren't fully developed, so gender prediction isn't reliable. You can try nub theory from your scan photo, but this is just for fun and isn't a medical prediction.

What if my baby is in the wrong position?

If your baby is lying in a position that makes measurement difficult, the sonographer may ask you to roll onto your side, cough, or walk around for a few minutes. Sometimes they'll ask you to come back later or on another day.

Further reading:

This article is for informational purposes only and does not constitute medical advice. Always consult your healthcare provider.

Last reviewed: June 2026

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