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A 35-year-old female asked:

Does 1st trimester ultrasound have margin of error up to 7 days because of the equipment/skill of tech or because fetus can grow at dif rates?

1 doctor answer1 doctor weighed in
Dr. Brad Douglas
Obstetrics and Gynecology 26 years experience
Margin of error is: Margin of error is 8% - so it differs the longer you are pregnant...so for example at 10 weeks - you are 70 days pregnant - which 8% means a 5 to 6 day error. If you are 20 weeks - the error is 140 days x 8% which is about 11 days of error .....so you need to do math
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Last updated Oct 21, 2018

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