Baby dating scan be wrong
Most scans are carried out by specially trained staff called 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 then be asked to lower your skirt or trousers to your hips and raise your top to your chest.The sonographer will put ultrasound gel on your tummy and tuck tissue paper around your clothing to protect it from the gel.The gel makes sure there is good contact between the machine and your skin. It is this probe that sends out ultrasound waves and picks them up when they bounce back.If you are overweight or your body tissue is dense, sometimes this can reduce the quality of the image because there is more tissue for the ultrasound waves to get through before they reach the baby.If it's difficult to get a good image, the scan may take longer or have to be repeated at another time.See What if a screening test shows a possible problem?
Having a scan in pregnancy is usually a happy event, but be aware that ultrasound scans may detect some serious abnormalities, so try to be prepared for that information.
The sonographer estimates when your baby is due (the estimated date of delivery, or EDD) based on the baby's measurements.