It's wonderful to see a little blob with a heartbeat that will become your baby. If you are unsure of the first day of your last period you will be offered a dating ultrasound when you are between 10 and 14 weeks pregnant.
But ultrasounds can also lift the lid on a few worries you might be having. The main reason for the ultrasound is to work out how many weeks pregnant you are, and to estimate your due date.
It records high-frequency sound waves that create an image (see Reference 4). The point of the scan is to work out how many weeks pregnant you are. Ectopic pregnancy and miscarriage: diagnosis and initial management CG 154. You may have calculated the length of your pregnancy from the first day of your last menstrual period (LMP). It may also help you to avoid feeling disappointed towards the end of your pregnancy if you think your baby is late when he's not. The scan can check that your baby's heart is beating nicely and that he's developing normally.