Could an abdominal ultrasound in the first trimester be off by a month, making me a month further along? all of my ultrasounds have given same edd.

Increase accuracy : Overtime the accuracy of the ultrasound increases. It may be unusual to be off by 4 weeks if changes are occurring. Tell your doctor of your concerns and ask to see the findings to determine edd changes. Hope this helps.

No: A first trimester ultrasound could be off by 4 to 10 days depending on when the ultrasound exam was dome.