Question 1

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 2

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 3

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 4

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 5

what is the margin for error of an ultrasound at 15 weeks? preg confirmed at about 11 wks, wouldn't us have been done then?

Accepted Answer

Fetal Ultrasound: An Ultrasound may be done prior to 18-21 weeks gestation if a patient is unsure of her dates or there is a question of whether the pregnancy is within the uterus and not ectopic, i.e. tubal pregnancy or.if the patient is having vaginal bleeding, ultrasound may be performed to confirm whether the fetus is still living. Otherwise, the first ultrasound is usually done at 18-21 weeks.

Question 6

if lmp and 12 week ultrasound correlate, would the u/s be considered more accurate since the lmp is known? or is there still 1 week margin of error?

Accepted Answer

+/-1 week.: First trimester sonography is more accurate than even certain menstrual dates due to inherent variation in ovulation. The degree of accuracy at 12 weeks is within a week of the true due date. Take Folic Acid 1-5 mg daily and good luck!

Question 7

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 8

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 9

would the gestational age of 12wks+4days @62mm be off by 1 week since ultrasounds have a margin of error of 1 week in the first trimester?

Accepted Answer

Estimates: Determination of gestational age is based on estimates determined by the last menstrual period and ultrasound.  There is a margin of error with ultrasound, but that does not mean that the gestational age is necessarily different by a week.  It means that the ultrasound estimate is 12w4d with a very high likelihood that the actual age is between 11+ to 13+ weeks.

Question 10

what is the error of margin for an ultrasound dating at 11 week 4 day, measuring the fetus crl at 4.8 cm?

Accepted Answer

Plus or minus, 5 day: The margin of error at that gestational age is typically + or minus 5 days.  That crl is definitely normal for that gestational age.

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Doctor answers about:

Margin of error at 9 weeks ultrasound

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:

What is the margin for error of an ultrasound at 15 weeks? preg confirmed at about 11 wks, wouldn't us have been done then?

A member asked:

If lmp and 12 week ultrasound correlate, would the u/s be considered more accurate since the lmp is known? or is there still 1 week margin of 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:

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:

Would the gestational age of 12wks+4days @62mm be off by 1 week since ultrasounds have a margin of error of 1 week in the first trimester?

A member asked:

What is the error of margin for an ultrasound dating at 11 week 4 day, measuring the fetus crl at 4.8 cm?

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