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A member asked:
Can an ultrasound be off by 5-7 days forwards? or backwards? or both??
5 doctors weighed in across 3 answers
Yes: people are different sizes as are fetuses. The age is based on a best guess based on size (which varies), so the estimate has some variability.
Answered 8/20/2014
3.8k views
Yes : Ultrasound dating is an estimate and has a margin of error usually of several says either way. The accuracy depends on when the ultrasound was performed and how many different measurements were made.
Answered 8/20/2014
3.8k views
Depends: An early ultrasound in the first trimester has an accuracy of 5-7 days in either direction, but as the pregnancy progresses, the accuracy decreases with increased gestational age, so that by late in the second trimester the accuracy can fall off to +/- 2 weeks. Typically ultrasound dating is done before 18-20 weeks for the most accuracy.
Answered 8/20/2014
3.8k views
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