6–11 Weeks: This baby scan is performed to establish the presence of a single or multiple intrauterine pregnancy. We look at the heartbeat and measure the embryo to determine the age. This early measurement is very accurate for dating. Anatomical details are limited at this stage

We use the first day of your last menstrual period to determine the gestational age. We compare that with specific measurements of the embryo by measuring the distance from the top of the head (crown) to the bottom of the body (rump). We may also include measurements of the gestational sac and of the heartbeat. These measurements are very accurate and can determine the expected age even if you are unsure of your last menstrual period.