However, some major problems can be seen at your dating scan, such as problems with your abdominal wall or with your baby's skull.You may need a second scan to check the first scan's findings.

Having a scan in the first few months of pregnancy can be a thrilling experience.

It's amazing to see the little blob with a heartbeat that will soon become your baby.

This measures a collection of fluid under the skin at the back of a baby's neck.

The dating scan will take between five minutes and 10 minutes.

This is because blood tests for Down syndrome are not very accurate if you are having more than one baby.

Instead, you will be offered a nuchal translucency (NT) scan.

After 13 weeks your baby can curl up and stretch out, so measuring the length becomes less accurate.

Then the circumference of the head becomes the best way to measure your baby Some hospitals and private clinics offer a dating and screening scan at the same time.

Looking for abnormalities isn't the purpose of this scan, though.