ultrasound dating

1st Trimester Ultrasound Dating

Jane Foley's picture

QUESTION

Dear Ms. Ultrasound,
Hello! Was hoping for your expert opinion regarding ultrasounds. Is it at all possible that a 9-week gestational age per ultrasound could be off by two weeks? (And I am not confused as to the "missing 2 weeks" in calculating gestational age.)

Basically, in mm or cm, how much bigger is an 11-week pregnancy compared to a 9-week pregnancy?

Thank you!