When is the best time in pregnancy to get an accurate dating scan? Our midwife At this time, it should be possible to see a heartbeat. Find out more about your 12 week dating scan. You should have your first pregnancy ultrasound scan in between 10 weeks and 13 weeks pregnant, but it can. of pregnancy, usually around 12 weeks, you should be offered a pregnancy dating scan. You may need to have a full bladder for this scan, as this makes the.