At this time, the fetus is a little larger and easier to measure. 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 early ultrasound be off by 2 weeks?

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.

How can you tell if your pregnant by your pulse?

You can measure your own heart rate by taking your pulse. To do so, place your index and middle fingers on the wrist of your other hand, just below your thumb. You should be able to feel a pulse. (You shouldnt use your thumb to take the measurement because it has a pulse of its own.)