A member 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?

A doctor has provided 1 answer
Dr. Brad Douglas answered

Specializes in Obstetrics and Gynecology

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

Answered 10/21/2018

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