It's wonderful to see the little blob with a heartbeat that will become your baby.
Usually two scans are done during the first trimester.
It is offered when you are around 11 to 14 weeks pregnant.
In some areas the dating scan and the NT scan will be carried out together.
However, if you did not get a first trimester ultrasound for dating and an ultrasound done to look at the baby's anatomy (usually at 18-20 weeks of pregnancy) differs from your LMP date by 10 to 14 days, we would change your date to the ultrasound estimate.