The dating scan is an ultrasound scan that can be done as early as six weeks after the last period, but the dating scan will be most accurate when done between 8 and 12 weeks gestation.

Can an ultrasound be wrong by 4 weeks?

Evidence suggests that ultrasounds more accurately predict your due date than using your last menstrual period—but only in the first trimester and early second trimester (until roughly 20 weeks). 3 Early ultrasound due dates have a margin of error of roughly 1.2 weeks.

How can you tell if your 4 weeks pregnant?

4 weeks pregnant symptomsbreast tenderness.exhaustion.frequent urination.nausea.heightened sense of taste or smell.food cravings or aversions.18 Oct 2017