Your Dating Scan: What Happens at the 12-Week Scan

The dating scan is one of the most anticipated appointments in early pregnancy. It's often the first time you see your baby, and for many parents, it's the moment everything becomes real. Here's what happens, what it checks, and how to prepare.

What is the dating scan?

The dating scan is an ultrasound examination offered by the NHS between weeks 11 and 14 of pregnancy (ideally between 11+2 and 14+1 weeks). Its primary purpose is to confirm how far along you are and calculate your estimated due date more accurately than a last menstrual period calculation.

What happens during the scan

The appointment usually takes 15-20 minutes. You'll lie on a couch with your abdomen exposed while a sonographer applies gel and moves an ultrasound probe across your belly. The gel feels cold but the scan itself is painless.

On the screen, you'll see your baby for the first time. At 12 weeks, they're about 5-6cm long and remarkably well-formed. You might see them wriggling, stretching, or even hiccupping.

If it's very early in the window (before 11 weeks), the scan may need to be done transvaginally. This gives a clearer image when baby is still very small.

What the sonographer checks

Crown-rump length (CRL). The measurement from the top of baby's head to their bottom. This is the most accurate way to determine gestational age.

Heartbeat. The sonographer confirms cardiac activity. At 12 weeks, the heart rate is typically 120-160 BPM.

Number of babies. This is when twin or multiple pregnancies are usually confirmed.

Basic anatomy. The sonographer checks that baby's skull, brain, limbs, and abdominal wall are developing normally.

Nuchal translucency (if you opt for combined screening). If you've consented to screening for Down's syndrome, Edwards' syndrome, and Patau's syndrome, the sonographer measures the fluid at the back of baby's neck. This measurement, combined with a blood test, gives a statistical probability rather than a diagnosis. The screening is optional.

How to prepare

Check whether you need a full bladder. Your appointment letter should tell you. A full bladder can help with the image by pushing the uterus up.

Wear practical clothing. A top and trousers/skirt is easier than a dress.

Bring your partner or support person. Most trusts allow one person to accompany you.

Write down questions. Common ones include: Is baby measuring on track? Is there anything you're concerned about? When will I get my due date?

Understanding the results

After the scan, you'll receive an updated due date. If this differs significantly from the date calculated from your last period, the scan date takes precedence.

If the combined screening test results in a higher probability, you'll be offered further tests for a definitive answer. A higher probability result doesn't mean there is a problem - it means further investigation is recommended.

If the scan shows a concern

In the vast majority of cases, dating scans are straightforward and reassuring. But occasionally, concerns are identified. A concern doesn't mean a problem. It means your care team is being thorough.

If further investigation is needed, your midwife will explain the next steps, what the findings mean, and what support is available.

Getting your scan photo

Most hospitals offer printed scan photos, sometimes for a small charge (typically 5-10). It's a lovely keepsake of the first time you saw your baby. You could say it's your baby's first portrait!