The dating scan, which is normally taken at around 12 weeks of pregnancy, is used to ascertain the age of the pregnancy and confirm the estimated date of delivery. Additionally, it is usually the woman's first image of her growing baby.
The dating scan is taken by a sonographer, who will use ultrasound to view the developing baby - and confirm whether it is a single or multiple pregnancy. Unlike earlier scans, the dating scan is not taken vaginally. Instead, it is carried out using a device that is placed over the woman's lower abdominal area to capture images of the foetus.
Once the image is available, the sonographer will take a series of measurements, which include the length of the baby from head to bottom. The sonographer will also check that the foetus has a heartbeat, and will also assess the overall development of the foetus.
While the dating scan is not designed to look for abnormalities, some significant developmental issues can be identified at this stage, depending on the equipment used and the experience of the sonographer. However, this is not the primary purpose of the dating scan, and a second scan at 20 weeks will capture in far more detail any problems with the developing foetus.
Most dating scans take around 10 minutes and women are advised to have a full bladder in time for the appointment. This helps to give a clearer picture of the baby. It is also advisable to take some loose change as most hospitals make a small charge for a hard copy of the images generated.