Can an estimated date of conception be wrong?
EDC stands for Estimated Date of CONFINEMENT, not conception. Of
course it could be wrong. It is just an estimate. If it is from a
doctor, be sure to take it into consideration, though. It may not
be perfect, but a medical expert's advice is always best to follow.
An ultrasound will give you a more accurate date if you are unsure
of your last period.