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How often are first trimester ultrasounds off in dating conception?

1 doctor weighed in
Dr. Gerard Honore
Fertility Medicine

In brief: Off?

Depends what you mean by 'off.
' the theoretical accuracy of a 1st trimester us is considered to be +/- 2-3 days, so in that sense they are always 'off.' if you mean wrong, as in more than 2-3 days, no one knows this - but with a skilled sonographer and a current us machine, it shouldn't be off by more than a few days very often.

In brief: Off?

Depends what you mean by 'off.
' the theoretical accuracy of a 1st trimester us is considered to be +/- 2-3 days, so in that sense they are always 'off.' if you mean wrong, as in more than 2-3 days, no one knows this - but with a skilled sonographer and a current us machine, it shouldn't be off by more than a few days very often.
Dr. Gerard Honore
Dr. Gerard Honore
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