Question 1

is the margin of error in a 1st trim ultrasound based on error of measurements or assigning a due date? i hear diff things about how "off" they can be

Accepted Answer

Gestational age: It is reported as number of days that gestational age could be off, in days.  Assuming that babies all mature similarly (a fairly good assumption within a week or two) this also applies to expected delivery date.

You have asked at least 3 questions about this topic.  I suggest you read something more definitive such as this http://www.Nlm.Nih.Gov/medlineplus/pregnancy.Html.

Question 2

how accurate is a 7 week ultrasound? any room for error?

Accepted Answer

Need more info.: Accurate for what? Determining viability or age of gestation? Regardless no test is '100%'.

Question 3

if ultrasounds have margin of error, how do u know when you're within the range of when the nt scan should be done?does fetus have to be certain size?

Accepted Answer

Best estimate : The margin of error for ultrasound dating is the smallest in the first trimester, which is when the nuchal translucency scans are performed. Yes the fetus does have to be a certain size and between certain dates in order for the information to be accurate.

Question 4

doctor said that a 12 week fetus couldn't be 2 weeks off and confused with an 8 or 10 week fetus.is there not a range of error with ultrasounds?

Accepted Answer

7 days: Two weeks is outside the margin of error of ultrasound at this gestation. I agree with your doctor.

Question 5

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?

Accepted Answer

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

Question 6

which is more accurate. an ultrasound at 5 weeks 5 days or 8 weeks 3 days? what would be the margin of error for the one most accurate?

Accepted Answer

Both: I'm not sure where you are going.  Both dates are very accurate for dating a fetus.  The margin of error is about a week

Question 7

if there is a 1wk margin of error for a 12 wk ultrasound, then would crl measurements of 62 mm be inaccurate? so i may have been 11or13wks, not 12wks?

Accepted Answer

No: If done correctly, shouldn't be off by more than 3 days or so.

Question 8

are 11week ultrasounds accurate for dating? margin of error?

Accepted Answer

Varies: The range of error for an ultrasound at that point would likely be around +/- 8 days.

Question 9

could conception occur outside of the +/- 1 week margin of error based on the ultrasound?

Accepted Answer

Yes if: 1) the pregnancy's abnormal and hence not the correct size, 2) the sonographer mismeasured or miscalculated. Otherwise, not really.

Question 10

how come there's a error of a week even with a early ultrasound! when it comes to conception?

Accepted Answer

Simple.: Because not all people are made the same and no test is perfect.  Generally it is not critical to have perfect dates.

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Doctor answers about:

Ultrasound errors

A member asked:

Is the margin of error in a 1st trim ultrasound based on error of measurements or assigning a due date? i hear diff things about how "off" they can be

A member asked:

How accurate is a 7 week ultrasound? any room for error?

A member asked:

If ultrasounds have margin of error, how do u know when you're within the range of when the nt scan should be done?does fetus have to be certain size?

A member asked:

Doctor said that a 12 week fetus couldn't be 2 weeks off and confused with an 8 or 10 week fetus.is there not a range of error with ultrasounds?

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 member asked:

Which is more accurate. an ultrasound at 5 weeks 5 days or 8 weeks 3 days? what would be the margin of error for the one most accurate?

A member asked:

If there is a 1wk margin of error for a 12 wk ultrasound, then would crl measurements of 62 mm be inaccurate? so i may have been 11or13wks, not 12wks?

A member asked:

Are 11week ultrasounds accurate for dating? margin of error?

A member asked:

Could conception occur outside of the +/- 1 week margin of error based on the ultrasound?

A member asked:

How come there's a error of a week even with a early ultrasound! when it comes to conception?

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