Ultrasound scans use sound waves to build a picture of the baby in the womb. The scans are painless, have no known side effects on mothers or babies, and can be carried out at any stage of pregnancy. Talk to your midwife, GP or obstetrician about any concerns you have.

Having a scan in pregnancy is usually a happy event, but be aware that ultrasound scans may detect some serious health conditions, so try to be prepared for that information.

What will happen at the scan?

Most scans are carried out by sonographers. The scan is carried out in a dimly lit room so the sonographer is able to get good images of your baby.

You'll be asked to lie on your back and reveal your tummy.

The sonographer will put ultrasound gel on your tummy, which makes sure there is good contact between the machine and your skin.

The sonographer passes a probe over your tummy and a picture of the baby will appear on the ultrasound screen.

During the exam, sonographers need to keep the screen in a position that gives them a good view of the baby.

The sonographer will carefully examine your baby's body. The sonographer may need to apply slight pressure on your tummy to get the best views of the baby.

How long will a scan take?

A scan usually takes around 20 to 30 minutes. However, the sonographer may not be able to get good views if your baby is lying in an awkward position or moving around a lot.

If it's difficult to get a good image, the scan may take longer or have to be repeated at another time.

Can an ultrasound scan harm me or my baby?

There are no known risks to the baby or the mother from having an ultrasound scan, but it's important that you consider carefully whether to have the scan or not.

This is because the scan can provide information that may mean you have to make further important decisions. For example, you may be offered further tests, such as amniocentesis, that have a risk of miscarriage.

When are scans offered?

This depends on where in the world you live. The first one will usually take place between 10 and 14 weeks, and a second one around 18 to 21 weeks.

The first scan is sometimes called the dating scan. The sonographer estimates when your baby is due (the estimated date of delivery, or EDD) based on the baby's measurements.

The dating scan can include a nuchal translucency (NT) scan, which is part of the combined screening test for Down's syndrome, if you choose to have this screening.

The second scan offered during pregnancy usually takes place between 18 and 21 weeks of pregnancy. It's sometimes called the mid-pregnancy scan. This scan checks for 11 physical conditions in your baby.

You may be offered more than 2 scans, depending on your health and the pregnancy.

Learn more:

• Places to deliver your baby
• High-risk pregnancy
• Blood type and rhesus test
• Gestational diabetes
• Iron deficiency anaemia
• Blood tests and scans
• Blood pressure tests
• Antenatal urine tests
• Weight and height checks in pregnancy