EDD or AUA, which date is more accurate?

Dear Ask The Doctor: What should I go by the edd or the aua?

Dear Tegan: It is difficult to say which date you should go by. Generally ultrasound dating is more accurate and earlier the ultrasound more the accuracy. But it really does not matter as the dates are pretty close. Generally I'd go with the EDD unless you're not sure of the LMP, in which case you may need to go with the AUA (average ultrasound age).