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A member asked:

Is first ultrasound or the second more accurate?

A doctor has provided 1 answer

Ultrasound dating: The first. First trimester ultrasound is accurate within 5-7 days. 2nd trimester ultrasound has accuracy of +/_ 2 weeks. Lmp dating also assumes a 28 day cycle. There is no test that can date conception more accurately than a 1 week window. Due date is based on LMP unless us off by more than 1 week 1st trimester or 2 weeks in 2nd.

Answered 2/13/2015

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Related Questions

A member asked:

My first ultrasound showed only a 9mm gest sac. 2 weeks later they could see the baby, measuring 7w1d. How accurate are these measurements for dating?

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A member asked:

If my first Ultrasound said 7weeks and 4 days and my second said 10 weeks and 2 days would be date of conception be accurate? When I put it in a calculator it said 6/19/2021 Date of Conception?

A doctor has provided 1 answer

A member asked:

What is the range of accuracy for an abdominal ultrasound in the first tri?

A doctor has provided 1 answer

A member asked:

Don't need to pinpoint conception day, but two first trim ultrasound give same due date we have no lmp to go off, how accurate is age of our baby?

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A member asked:

Only possible conception dates: 7/4 and 7/18-23rd my first ultrasound dated me at 13 weeks 5 days.With a conception date of 7/20.How accurate is this?

A doctor has provided 1 answer

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