Even dating scans can be inaccurate for the due date, but they are never as inaccurate as using the menstrual period. For instance a dating scan done at 6 weeks could get the date wrong five days either way.
Can a dating ultrasound be off by a month?
As pregnancy progresses, the accuracy of an ultrasound for predicting due dates decreases. Between 18 and 28 weeks of gestation, the margin of error increases to plus or minus two weeks. After 28 weeks, the ultrasound may be off by three weeks or more in predicting a due date.
Are you really pregnant at 2 weeks?
So at 2 weeks pregnant, youre actually not pregnant. But you may be close! If youre preparing to try to get pregnant, keep your eyes open for signs of ovulation and do that thing you do to get pregnant—have plenty of sex around the time you expect to ovulate.