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1st Trimester Ultrasound Dating

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!

ANSWER

Hello
An early first trimester ultrasound will not be off two weeks. It may be off two days, but not two weeks!

If you are wondering about a conception date you might let me know the date of the ultrasound and how many weeks and days you were at the time of the ultrasound. If there are specific possible conception dates you are wondering about let me know those too. We then can scientifically go through possibilities.

With Regards,
-- Jane RDMS

Jane Foley

Jane Foley has worked as a Sonographer (Ultrasound Technologist) since 1979. Jane has lived and worked in many parts of the world including Saudi Arabia. She is a Registered Diagnostic Medical Sonographer or RDMS. She pulls a wealth of information from her experience in the field of Radiology and her interactions with such a broad cross-section of cultures she has visited. She now makes her home on the island of Maui with her English husband, Michael.