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Doctor insights on: Does Ultrasound Measure Gestational Age

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Do ultrasounds measure fetal or gestational age? And how accurate are they at 7 weeks 5 days?

Do ultrasounds measure fetal or gestational age? And how accurate are they at 7 weeks 5 days?

Yes. "Accurate".: Ultrasound pregnancy dating scans measure fetal size or age (time since conception), and convert the measurements to human gestational age. Gestational age is calculated by adding 2 weeks to the age of the fetus (to the time since conception), and roughly represents the total weeks since the first day of the last menstrual period (LMP). All dates are ESTIMATES, so 7w 5d means about 7w to 8w 3d. ...Read more

Dr. Michael Gabor
2,275 Doctors shared insights

Sonogram (Definition)

An ultraound, also known as a sonogram, is a painless and relatively inexpensive imaging test that utilizes sound waves instead of ionizing radiation. There are no side effects. Ultrasound can give us two-dimensional, and in some applications three-dimensional, images of structures and organs in virtually any part of the body. In addition to diagnostic uses, such as evaluating abnormalities in the abdomen, pelvis, and breast, ultrasounds are commonly used to guide needle and catheter placement in a variety of surgical ...Read more


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Can first trimester dating ultrasounds be a month off gestational age? (if taken at 8 weeks) could I have been 13 weeks and they measured 8?

Can first trimester dating ultrasounds be a month off gestational age? (if taken at 8 weeks) could I have been 13 weeks and they measured 8?

Unlikely: Ultrasound dating is very accurate when done around 8-11 weeks of gestation. But, as always, life is not perfect and mistakes can happen. A woman should be able remember what she was doing 6 weeks ago (around the time of conception) if the u/s scan is showing 8 weeks gestation. ...Read more

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Do ultrasounds measure from gestational age or does it measure from the day of conception? I have an extremely irregular period..

Do ultrasounds measure from gestational age or does it measure from the day of conception? I have an extremely irregular period..

Ultrasound: Measurements estimate the gestational age of the fetus. Gestational age is in relation to your last menstrual period. For example, a fetus measuring 8 weeks gestation on ultrasound would have been conceived 6 weeks prior to the ultrasound. A patient with 28 day cycles would have started her last menstrual period 8 weeks prior to the scan. Keep in mind that these measurements are estimates. ...Read more

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Is gestational age accurate from ultrasound at 9 weeks?

Is gestational age accurate from ultrasound at 9 weeks?

Yes it is: By that point, ultrasound is the primary tool to estimate gestational age. More accurate than last menstrual period. ...Read more

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Don't ultrasounds start gestational age from your LMP date?

Don't ultrasounds start gestational age from your LMP date?

Yes: All pregnancies are dated from the first day of the last menstrual period but an early ultrasound is more precise and may change the due date if greater than a 5 day difference. Gd luc. ...Read more

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How accurate is gestational age at 13 weeks via ultrasound?

About 7 days: First trimester ultrasounds are the most accurate, but a 13 week ultrasound should be quite good at estimating the due date. Best of luck! ...Read more

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Are ultrasounds a very accurate indicator of gestational age?

Are ultrasounds a very accurate indicator of gestational age?

Earlier the better: The accuracy of ultrasound diminishes with the age of the fetus. The most accurate dating is in the first 4-6 weeks. ...Read more

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Is conception usually two weeks after gestational age from ultrasound?

Yes: That's basically correct, it's close to 2 weeks. Ultrasound dating is calculated as if it's from a 'theoretical' last menstrual period, so actual conception would be around 2 weeks after. ...Read more

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Can measurements taken from an ultrasound lead to a wrong estimation of gestational age?

Can measurements taken from an ultrasound lead to a wrong estimation of gestational age?

Yes: An ultrasound done in the first trimester will be accurate to within a week of the due date. In fact don't think of it as a due date, but more as a due week as 90% of women will have their baby one week around their due date. Ultrasounds in the second and third trimester will be accurate to within 2-3 weeks of the due date. ...Read more

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Does gestational age achieved from an early ultrasound assume ovulation occured around cd 14?

Does gestational age achieved from an early ultrasound assume ovulation occured around cd 14?

In a way: First trimester ultrasound is based on measurements only, which is extremely reliable. No assumption need be made. The ega is reported from the first day of a hypothetical last menstrual period; so in that regard it 'assumes' conception on cd 14. ...Read more

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Is a gestational age reading accurate on a 10 week ultrasound? And what exactly are they measuring?

Is a gestational age reading accurate on a 10 week ultrasound? And what exactly are they measuring?

Accurate: A first trimester ultrasound is highly accurate. They are measuring what is called a crown (top of the head) rump (bottom of the bum) length. The length is compared to average size embryos to come up with a gestational age. ...Read more

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My LMP is 26-5-2017, but today my ultrasound shows gestational age of 5 weeks and 6 days... is it normal?

My LMP is 26-5-2017, but today my ultrasound shows gestational age of 5 weeks and 6 days... is it normal?

Yes it can be: Normal - you may have been fertilized right before your menstrual period in June was due - so that would put the conception 5-6 weeks ago. I would not worry about the gestational age, be ecstatic for yourself and your partner and the wonderful child that is coming to this world. Thanks for trusting in HealthTap. ...Read more

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Can a ultrasound in gestational age at 19 weeks be off by + -- 25 days I know it can be off +- 7 to 10 days but what about 25 days?

Can a ultrasound in gestational age at 19 weeks be off by + -- 25 days I know it can be off +- 7 to 10 days but what about 25 days?

No: If you had a competent ultrasonographer with a good ultrasound machine, it shouldn't be off by more than 10 days. (Remember that pregnancy dating isn't based on the actual date of conception but is based on the last menstrual period, which is 2 weeks prior to conception. Saying it another way, if the ultrasound says 19 weeks, conception happened 17 weeks prior +/- 10 days.) Best wishes! ...Read more

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Why are my ultrasounds always a week ahead of my period gestational age?

Why are my ultrasounds always a week ahead of my period gestational age?

Natural fluctuation: Woman's ovulatory cycle is on lunar calender. So the gap builds up with regular calender calculation. ...Read more

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How to find out conception date from ultrasound gestational age?

How to find out conception date from ultrasound gestational age?

Internet: Go to this website it will help you figure it out
http://www. Babymed. Com/conception-calculator. ...Read more

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Ultrasound on august 7 said gestational age was 7 weeks, 5 days. Crl 1.44cm. When did I conceive?

Ultrasound on august 7 said gestational age was 7 weeks, 5 days. Crl 1.44cm. When did I conceive?

Approx 6/28/12: Give or take a few days. Edc is calculated to march 21, 2013. Congrats. ...Read more

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Do doctors go by gestational age or conception date during ultrasounds? My dates are off by about a week and a half.

Do doctors go by gestational age or conception date during ultrasounds? My dates are off by about a week and a half.

Gestational age: Ultrasound is more accurate in determining gestational age than the date of your last period. ...Read more

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Which gestational age is more accurate, LMP based or ultrasound one? By LMP I am 27weeks and 4 days. Ultrasound says 28 weeks

Which gestational age is more accurate, LMP based or ultrasound one? By LMP I am 27weeks and 4 days. Ultrasound says 28 weeks

Gestational age: Your LMP is usually more accurate than ultrasound especially at 27+ weeks. Ultrasound is more accurate in the first trimester and gets less accurate the further along you get in the pregnancy. ...Read more

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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?

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. ...Read more

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Can a first trimester ultrasound gestational age/edd be wrong by 7 weeks?

No: First trimester ultrasounds are the most accurate for estimating gestational age within +/- 7 days. ...Read more

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How accurate are 1st trimester ultrasounds in estimating gestational age? What about 2nd trimester ultrasounds?

How accurate are 1st trimester ultrasounds in estimating gestational age? What about 2nd trimester ultrasounds?

Accurate!: 1st trimester ultrasounds are very accurate - have correlated with timed ivf pregnancies.
We usually consider 1st trimester scans accurate within 5-7days' 2nd trimester scans within 10-14days. ...Read more

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Transvag ultrasound @ 6wk3d shows good heartbeat but gestational sac measures smaller (1.6cm) and is cloudy. What could this mean?

Heartbeat: Seeing the heartbeat greatly proves the odds that pregnancy will not miscarry. I haven't heard of someone saying the sac was 'cloudy' before. Sac size --inform differs from your LMP -- is okay. Just means you ovulated at different time. I would ask for another ultrasound in 2-3 weeks if you're worried, but also know that good heartbeat means a lot. ...Read more

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Week on ultrasound picture is gestational age or fetal age.?

Week on ultrasound picture is gestational age or fetal age.?

Both: Fetal age is of course the exact age of your fetus as determined by measurements taken of the baby. Fetuses have different rates of growth or may have problems with growth, so sometimes the measurement age doesn't match the "expected" gestational age. The best "age" is determined by an early ultrasound between 6 and 12 weeks gestation. Accuracy of ultrasound decreases as pregnancy progresses. ...Read more

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Can a 7-8 week vaginal ultrasound be a month off with dating the gestational age/due date?

Not likely: A 7-8 week vaginal sono should be within a week of the actual date of conception plus 2 weeks. The gestational age is expressed as weeks since last menstrual period (lmp) and assumes conception 2 weeks later. If you are 4 weeks less than expected you conceived one cycle later. Due date is an estimate of 40 weeks since the LMP and assumes you will carry full term and not be late or preterm. ...Read more

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Can conception range be over a week off if gestational age is confirmed by early first trimester ultrasound?

Yes: In general, ultrasound established dates should take precedence over menstrual dates if the discrepancy is greater than 7 days if done in the first trimester (first 12 weeks) and more than 10 days if done in the second trimester. ...Read more