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A 32-year-old female asked:

Hi i am 26 wks and all mu ultrasounds have the same edd of 9/13 could it be off a few days or is it accurate to say i conceived on 12/22?

2 doctor answers2 doctors weighed in
Dr. Derek Haas
Specializes in Fertility Medicine
Yes, can be off few: The earlier the first dating sonogram was, the more accurate the due date will be. A sonogram at 6-11 weeks is ideal for accurately measuring the fetus which gives you the due date. Having said that, you can still be off by up to 7 days.
Created for people with ongoing healthcare needs but benefits everyone.
Dr. Charles Whiting
Obstetrics and Gynecology 28 years experience
+/- a week or so: Ultrasound due dates are not precise. How accurate they are depends on how early the first U/S was done. An ultrasound at 8 weeks, for example, can be off by up to 5 days. An ultrasound at 12 weeks, may be off by a week. An ultrasound in the second trimester can be off by 2 weeks. Since the conception date is calculated from the ultrasound date, it could be off by the same number of days.
Created for people with ongoing healthcare needs but benefits everyone.
Last updated Jun 13, 2016

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